FOOD FATS AND OILS

___________________________

Institute of Shortening and Edible Oils 1750 New York Avenue, NW, Suite 120

Washington, DC 20006

Phone 202-783-7960 Fax 202-393-1367

www.iseo.org

Eighth Edition

Prepared by the Technical Committee of the Institute of Shortening and Edible Oils, Inc.

Ed Campbell, Chairman Nick Baker Maury Bandurraga Maurice Belcher Carl Heckel Allan Hodgson Jan Hughes Tony Ingala Dan Lampert Earniie Louis Don McCaskill Gerald McNeill Mark Nugent Ed Paladini Judy Price Ram Reddy Joe Sharp Stan Smith Dennis Strayer Bob Wainwright Laura Waldinger

First edition -- 1957 Second edition -- 1963 Third edition -- 1968 Fourth edition -- 1974 Fifth edition -- 1982 Sixth edition -- 1988 Seventh edition -- 1994 Eighth edition -- 1999

© 1999 by the Institute of Shortening and Edible Oils, Inc. Additional copies of this publication may be obtained upon request from the Institute of Shortening and Edible Oils, Inc., 1750 New York Avenue, NW, Washington, DC 20006.

PREFACE This publication has been prepared to provide useful information to the public regarding the nutritive and functional values of fats in the diet, the composition of fats and answers to the most frequently asked questions about fats and oils. It is intended for use by consumers, nutritionists, dieticians, physicians, food technologists, food industry representatives, students, teachers, and others having an interest in dietary fats and oils. Additional detail may be found in the references listed at the end of the publication which are arranged in the order of topic discussion. A glossary is also provided. The Institute of Shortening and Edible Oils, Inc. gratefully acknowledges the assistance of Judith Putnam, Economic Research Service, Human Nutrition Information Service, U.S. Department of Agriculture for providing data on the availability (or disappearance) of fats and oils in foods and Ed Hunter, Ph.D., consultant, for his assistance in writing this publication.

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Table of Contents Preface ................................................................................................... i

I. Importance of Fats .................................................................................1 II. What is a fat?..........................................................................................1 III. Chemical Composition of Fats...............................................................1 A. The Major Component – Triglycerides ...........................................1 B. The Minor Components ...................................................................2 1. Mono- and Diglycerides ..............................................................2 2. Free Fatty Acids...........................................................................2 3. Phosphatides ................................................................................2 4.Sterols ...........................................................................................2 5.Fatty Alcohols...............................................................................2 6.Tocopherols ..................................................................................2 7. Carotenoids and Chlorophyll.......................................................2 8.Vitamins .......................................................................................2 IV. Fatty Acids .............................................................................................3 A. General .............................................................................................3 B. Classification of Fatty Acids............................................................3 1. Saturated Fatty Acids ...................................................................3 2. Unsaturated Fatty Acids...............................................................3 3. Polyunsaturated Fatty Acids ........................................................4 C. Isomerism of Unsaturated Fatty Acids.............................................4 I. Geometric Isomerism....................................................................4 2. Positional Isomerism....................................................................5 V. Nutritional Aspects of Fats and Oils ......................................................6 A. General .............................................................................................6 B. Metabolism of Fats and Oils ............................................................6 C. Essential Fatty Acids........................................................................6 D. Fat Level in the Diet.........................................................................7 E. Diet and Cardiovascular Disease .....................................................7 F. Diet and Cancer................................................................................9 G. Health Effects of Trans Fatty Acids from Hydrogenation .............11 H. Areas of Current Research Interest ................................................13 I. Nonallergenicity of Edible Oils .....................................................14 J. Biotechnology ................................................................................14 K. Fat Reduction in Foods ..................................................................15 VI. Factors Affecting Physical Characteristics of Fats and Oils ................16 A. Degree of Unsaturation of Fatty Acids ..........................................16 B. Length of carbon Chains in Fatty Acids.........................................17 C. Isomeric Forms of Fatty Acids.......................................................17 D. Molecular Configuration of Triglycerides .....................................17 E. Polymorphism of Fats ....................................................................18

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VII. Processing ...........................................................................................18 A. General...........................................................................................18 B. Degumming ...................................................................................18 C. Refining .........................................................................................18 D. Bleaching .......................................................................................19 E. Deodorization.................................................................................19 F. Fractionation (including Winterization).........................................19 G. Hydrogenation ...............................................................................19 H. Interesterification ...........................................................................20 I. Esterification..................................................................................20 J. Emulsifiers .....................................................................................21 K. Additives and Processing Aids ......................................................21 VIII. Reactions of Fats and Oils ....................................................................23 A. Hydrolysis of Fats ..........................................................................23 B. Oxidation of Fats............................................................................23 1. Autoxidation...............................................................................23 2. Oxidation at Higher Temperatures.............................................23 C. Polymerization of Fats ...................................................................23 D. Reactions during Heating and Cooking .........................................24 IX. Products Prepared from Fats and Oils..................................................25 A. General ...........................................................................................25 B. Salad and Cooking Oils..................................................................27 C. Shortenings (Baking and Frying Fats) ...........................................28 D. Hard Butters ...................................................................................28 E. Margarine and Spreads...................................................................29 F. Butter..............................................................................................29 G. Dressings for Food .........................................................................29 1. Mayonnaise and Salad Dressing ................................................29 2. Pourable-Type Dressings ...........................................................29 3. Reduced Calorie Dressings ........................................................29 4. Reduced Fat, Low Fat, and Fat Free Dressings..........................30 H. Toppings, Coffee Whiteners, Confectioners’ Coatings and Other Formulated Foods..........................................................30 I. Lipids for Special Nutritional Applications ...................................30 X. Trends in Fat Consumption..................................................................30 XI. Conclusion ...........................................................................................32 References ............................................................................................33 Glossary ...............................................................................................36 Common Test Methods and Related Terms.........................................40

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Food Fats and Oils The oils and fats most frequently used in the

U.S. for salad and cooking oils, shortenings, margarines, salad dressings and food ingredients include soybean, corn, cottonseed, palm, peanut, olive, safflower, sunflower, canola, coconut, palm kernel, lard, and beef tallow. More detailed information on the use of some of these oils in specific products is provided in Section IX. Specialized vegetable oils of lesser availability in the U.S. include rice bran, shea nut, illipe, and sal.

I. IMPORTANCE OF FATS

Fats and oils are recognized as essential nutrients in both human and animal diets. They provide the most concentrated source of energy of any foodstuff, supply essential fatty acids (which are precursors for important hormones, the prostaglandins), contribute greatly to the feeling of satiety after eating, are carriers for fat soluble vitamins, and serve to make foods more palatable. Fats and oils are present in varying amounts in many foods. The principal sources of fat in the diet are meats, dairy products, poultry, fish, nuts, and vegetable fats and oils. Most vegetables and fruits consumed as such contain only small amounts of fat. Recent data from the U.S. Department of Agriculture (1) suggests that actual fat consumption currently is about 33% of total calories. A knowledge of the chemical composition of fats and oils and the sources from which they are obtained is essential in understanding nutrition and biochemistry.

III. CHEMICAL COMPOSITION OF FATS Triglycerides are the predominant component of most food fats and oils. The minor components include mono- and diglycerides, free fatty acids, phosphatides, sterols, fatty alcohols, fat-soluble vitamins, and other substances.

A. The Major Component – Triglycerides A triglyceride is composed of glycerol and three fatty acids. When all of the fatty acids in a triglyceride are identical, it is termed a “simple” triglyceride. The more common forms, however, are the “mixed” triglycerides in which two or three kinds of fatty acids are present in the molecule. Illustrations of typical simple and mixed triglyceride molecular structures are shown below.

II. WHAT IS A FAT?

Fats and oils are chemical units commonly called “triglycerides” resulting from the combination of one unit of glycerol with three units of fatty acids. They are insoluble in water but soluble in most organic solvents. They have lower densities than water, and at normal room temperatures range in consistency from liquids to solids. When solid appearing they are referred to as “fats” and when liquid they are called “oils.”

H2COO-C-R1 (Fatty Acid1) HCOO-C-R1 (Fatty Acid1) H2COO-C-R1 (Fatty Acid1)

S i mp l e T r i g lyc e r i d e The term “lipids” embraces a variety of

chemical substances. In addition to triglycerides, it also includes mono- and diglycerides, phosphatides, cerebrosides, sterols, terpenes, fatty alcohols, fatty acids, fat-soluble vitamins, and other substances.

H2COO-C-R1 (Fatty Acid1) HCOO-C-R2 (Fatty Acid2) H2COO-C-R3 (Fatty Acid3)

M i x e d T r i g l y c e r i d e

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The fatty acids in a triglyceride define the properties of the molecule and are discussed in greater detail in Section IV.

B. The Minor Components

1. Mono- and Diglycerides Mono- and diglycerides are mono- and diesters of fatty acids and glycerol. They are used frequently in foods as emulsifiers. They are prepared commercially by the reaction of glycerol and triglycerides or by the esterification of glycerol and fatty acids. Mono- and diglycerides are formed in the intestinal tract as a result of the normal digestion of triglycerides. They also occur naturally in very minor amounts in both animal fats and vegetable oils. R1-COO-CH2 HO-CH2 HO-CH R1-COO-CH

HO-CH2 HO-CH2

1 (or α)-Monoglyceride 2 (or β)-Monoglyceride R2-COO-CH2 R2-COO-CH2 R1-COO-CH HO-CH

HO-CH2 R1-COO-CH2

1 , 2 - Di g l y ce r id e 1 , 3 - Di g l y ce r id e

2. Free Fatty Acids As the name suggests, free fatty acids are the unattached fatty acids present in a fat. Some unrefined oils may contain as much as several percent free fatty acids. The levels of free fatty acids are reduced in the refining process discussed in Section VII. Refined fats and oils ready for use as foods usually have a free fatty acid content of only a few hundredths of one percent.

3. Phosphatides Phosphatides consist of alcohols (usually glycerol), combined with fatty acids, phosphoric acid, and a nitrogen-containing compound. Lecithin and cephalin are common phosphatides found in edible fats. For all practical purposes, refining removes the phosphatides from the fat or oil.

4. Sterols Sterols, also referred to as steroid alcohols, are a class of substances that contain the common steroid

nucleus plus an 8 to 10 carbon side chain and an alcohol group. Although sterols are found in both animal fats and vegetable oils, there is a substantial difference biologically between those occurring in animal fats and those present in vegetable oils. Cholesterol is the primary animal fat sterol and is only found in vegetable oils in trace amounts. Vegetable oil sterols collectively are termed “phytosterols.” Sitosterol and stigmasterol are the best-known vegetable oil sterols. The type and amount of vegetable oils sterols vary with the source of the oil.

5. Fatty Alcohols Long chain alcohols are of little importance in most edible fats. A small amount esterified with fatty acids is present in waxes found in some vegetable oils. Larger quantities are found in some marine oils.

6. Tocopherols Tocopherols are important minor constituents of most vegetable fats. They serve as antioxidants to retard rancidity and as sources of the essential nutrient vitamin E. There are four types of tocopherols varying in antioxidation and vitamin E activity. Among tocopherols, alpha-tocopherol has the highest vitamin E activity and the lowest antioxidant activity. Tocopherols, naturally occurring in most vegetable fats, may be partially removed by processing. They are not present in appreciable amounts in animal fats. These or other antioxidants may be added after processing to improve oxidative stability in finished products.

7. Carotenoids and Chlorophyll Carotenoids are color materials occurring naturally in fats and oils. Most range in color from yellow to deep red. Chlorophyll is the green coloring matter of plants which plays an essential part in the photosynthetic process. At times, the naturally occurring level of chlorophyll in oils may be sufficient for the oils to be tinged green. The levels of most of these color bodies are reduced during the normal processing of oils to give them acceptable color, flavor, and stability.

8. Vitamins Generally speaking, most fats and oils are not good sources of vitamins other than vitamin E. The fat-soluble vitamins A and D sometimes are added to foods which contain fat because they serve as good carriers and are widely consumed. For example, vitamin A is

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Saturated and unsaturated linkages are illustrated below:

included in the federal standard for margarine, and the vitamins A and D are included in the federal standard for Grade A milk.

IV. FATTY ACIDS

A. General Triglycerides are comprised predominantly of fatty acids present in the form of esters of glycerol. One hundred grams of fat or oil will yield approximately 95 grams of fatty acids. Both the physical and chemical characteristics of fats are influenced greatly by the kinds and proportions of the component fatty acids and the way in which these are positioned on the glycerol molecule. The predominant fatty acids are saturated and unsaturated carbon chains with an even number of carbon atoms and a single carboxyl group as illustrated in the general structural formula for a saturated fatty acid given below:

Saturated Bond

Unsaturated Bond

When the fatty acid contains one double bond it is called “monounsaturated.” If it contains more than one double bond, it is called “polyunsaturated.” In the International Union of Pure and Applied Chemistry (IUPAC) system of nomenclature, the carbons in a fatty acid chain are numbered consecutively from the end of the chain, the carbon of the carboxyl group being considered as number 1. By convention, a specific bond in a chain is identified by the lower number of the two carbons that it joins. In oleic acid (cis-9-octadecenoic acid), for example, the double bond is between the ninth and tenth carbon atoms.

CH3-(CH2)xCOOH

Unsaturated carbon chain carboxyl group Edible oils also contain minor amounts of branched chain and cyclic acids. Also odd number straight chain acids are typically found in animal fats. Another system of nomenclature in use for

unsaturated fatty acids is the “omega” or “n minus” classification. This system is often used by biochemists to designate sites of enzyme reactivity or specificity. The terms “omega” or “n minus” refer to the position of the double bond of the fatty acid closest to the methyl end of the molecule. Thus, oleic acid, which has its double bond 9 carbons from the methyl end, is considered an omega-9 (or an n-9) fatty acid. Similarly, linoleic acid, common in vegetable oils, is an omega-6 (n-6) fatty acid because its second double bond is 6 carbons from the methyl end of the molecule (i.e., between carbons 12 and 13 from the carboxyl end). Eicosapentaenoic acid, found in many fish oils, is an omega-3 (n-3) fatty acid. Alpha-linolenic acid, found in certain vegetable oils, is also an omega-3 (n-3) fatty acid.

B. Classification of Fatty Acids Fatty acids occurring in edible fats and oils are classified according to their degree of saturation. 1. Saturated Fatty Acids. Those containing only single carbon-to-carbon bonds are termed “saturated” and are the least reactive chemically. The saturated fatty acids of practical interest are listed in Table I by carbon chain length and common name. All but acetic acid occur naturally in fats. The principal fat sources of the naturally occurring saturated fatty acids are included in the table. The melting point of saturated fatty acids increases with chain length. Decanoic and longer chain fatty acids are solids at normal room temperatures. When two fatty acids are identical except for the

position of the double bond, they are referred to as positional isomers. Fatty acid isomers are discussed at greater length in subparagraph C of this section.

2. Unsaturated Fatty Acids. Fatty acids containing one or more carbon-to-carbon double bonds are termed “unsaturated.” Some unsaturated fatty acids in food fats and oils are shown in Table II. Oleic acid (cis-9-octadecenoic acid) is the fatty acid that occurs most frequently in nature.

Because of the presence of double bonds, unsaturated fatty acids are more reactive chemically than

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are saturated fatty acids. This reactivity increases as the number of double bonds increases.

With the bonds in a conjugated position, there is a further increase in certain types of chemical reactivity. For example, fats are much more subject to oxidation and polymerization when bonds are in the conjugated position.

Although double bonds normally occur in a non-conjugated position, they can occur in a conjugated position (alternating with a single bond) as illustrated below: 3. Polyunsaturated Fatty Acids. Of the

polyunsaturated fatty acids, linoleic, linolenic, arachidonic, eicosapentaenoic, and docosahexaenoic acids containing respectively two, three, four, five, and six double bonds are of most interest. The nutritional importance of these fatty acids is discussed in Section V, Part C, “Essential Fatty Acids.”

Conjugated

Vegetable oils are the principal sources of linoleic and linolenic acids. Arachidonic acid is found in small amounts in lard, which also contains about 10% of linoleic acid. Fish oils contain large quantities of a variety of longer chain fatty acids having three or more double bonds including eicosapentaenoic and docosahexaenoic acids.

Non-conjugated

TABLE 1 SATURATED FATTY ACIDS

Systematic Name

Common Name

No. of Carbon Atoms*

Melting Point °C

Typical Fat Source

Ethanoic Acetic 2 -- -- Butanoic Butyric 4 -7.9 Butterfat Hexanoic Caproic 6 -3.4 Butterfat Octanoic Caprylic 8 16.7 Coconut oil Decanoic Capric 10 31.6 Coconut oil Dodecanoic Lauric 12 44.2 Coconut oil Tetradecanoic Myristic 14 54.4 Butterfat, coconut oil Hexadecanoic Palmitic 16 62.9 Most fats and oils Octadecanoic Stearic 18 69.6 Most fats and oils Eicosanoic Arachidic 20 75.4 Peanut oil Docosanoic Behenic 22 80.0 Peanut oil *A number of saturated odd and even chain acids are present in trace quantities in many fats and oils.

C. Isomerism of Unsaturated Fatty Acids Isomers are two or more substances composed of the same elements combined in the same proportions but differing in molecular structure. The two important types of isomerism among fatty acids are (1) geometric and (2) positional. 1. Geometric Isomerism. Unsaturated fatty acids can exist in either the cis or trans form depending on the configuration of the hydrogen atoms attached to

the carbon atoms joined by the double bonds. If the hydrogen atoms are on the same side of the carbon chain, the arrangement is called cis. If the hydrogen atoms are on opposite sides of the carbon chain, the arrangement is called trans, as shown by the following diagrams. Conversion of cis isomers to corresponding trans isomers result in an increase in melting points as shown in Table II.

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Diagram I. A comparison of cis and trans molecular arrangements.

cis

trans

TABLE II SOME UNSATURATED FATTY ACIDS IN FOOD FATS AND OILS

Systematic Name

Common Name

No. of Double Bonds

No. of Carbon Atoms

Melting Point °C

Typical Fat Source

9-Decenoic Caproleic 1 10 - Butterfat 9-Dodecenoic Lauroleic 1 12 - Butterfat 9-Tetradecenoic Myristoleic 1 14 18.5 Butterfat 9-Hexadecenoic Palmitoleic 1 16 - Some fish oils, beef fat 9-Octadecenoic Oleic 1 18 16.3 Most fats and oils 9-Octadecenoic* Elaidic 1 18 43.7 Partially hydrogenated

oils 11-Octadecenoic* Vaccenic 1 18 44 Butterfat 9,12-Octadecadienoic Linoleic 2 18 -6.5 Most vegetable oils 9,12,15-Octadecatrienoic Linolenic 3 18 -12.8 Soybean oil, canola oil 9-Eicosenoic Gadoleic 1 20 - Some fish oils 5,8,11,14-Eicosatetraenoic Arachidonic 4 20 -49.5 Lard 5,8,11,14,17-Eicosapentaenoic - 5 20 - Some fish oils 13-Docosenoic Erucic 1 22 33.4 Rapeseed oil 4,7,10,13,16,19-Docosahexaenoic - 6 22 - Some fish oils *All double bonds are in the cis configuration except for elaidic acid and vaccenic acid which are trans. Elaidic and oleic acids are geometric isomers; in the former, the double bond is in the trans configuration and in the latter, in the cis configuration. Generally speaking, cis isomers are those naturally occurring in food fats and oils. Trans isomers occur naturally in ruminant animals

such as cows, sheep and goats and also result from the partial hydrogenation of fats and oils. 2. Positional Isomerism. In this case, the location of the double bond differs among the isomers.

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Petroselinic acid, which is present in parsleyseed oil, is cis-6-octadecenoic acid and a positional isomer of oleic acid, cis-9-octadecenoic acid. Vaccenic acid, which is a minor acid in tallow and butterfat, is trans-11-octadecenoic acid and is both a positional and geometric isomer of oleic acid. The position of the double bonds affects the melting point of the fatty acid to a limited extent. Shifts in the location of double bonds in the fatty acid chains as well as cis-trans isomerization may occur during hydrogenation. The number of positional and geometric isomers increases with the number of double bonds. For example, with two double bonds, the following four geometric isomers are possible: cis-cis, cis-trans, trans-cis, and trans-trans. Trans-trans dienes, however, are present in only trace amounts in partially hydrogenated fats and thus are insignificant in the human food supply. V. NUTRITIONAL ASPECTS OF FATS AND OILS

A. General Fats are a principal and essential constituent of the human diet along with carbohydrates and proteins. Fats are a major source of energy which supply about 9 calories per gram. Proteins and carbohydrates each supply about 4 calories per gram. In calorie deficient situations, fats together with carbohydrates spare protein and improve growth rates. Some fatty foods are sources of fat-soluble vitamins, and the ingestion of fat improves the absorption of these vitamins regardless of their source. Fats are vital to a palatable and well-rounded diet and provide the essential fatty acids, linoleic and linolenic. B. Metabolism of Fats and Oils In the intestinal tract, dietary triglycerides are hydrolyzed to 2-monoglycerides and free fatty acids. These digestion products, together with bile salts, aggregate and move to the intestinal cell membrane. There the fatty acids and the monoglycerides are absorbed into the cell and the bile acid is retained in the intestines. Most dietary fats are 95-100% absorbed. In the intestinal wall, the monoglycerides and free fatty acids are recombined to form triglycerides. If the fatty acids have a chain length of ten or fewer carbon atoms, these acids are transported via the portal vein to the liver where they are metabolized rapidly. Triglycerides containing fatty acids having a chain length of more than ten carbon atoms are transported via the lymphatic system. These triglycerides, whether coming from the

diet or from endogenous sources, are transported in the blood as lipoproteins. The triglycerides are stored in the adipose tissue until they are needed as a source of calories. The amount of fat stored depends on the caloric balance of the whole organism. Excess calories, regardless of whether they are in the form of fat, carbohydrate, or protein, are stored as fat. Consequently, appreciable amounts of dietary carbohydrate and some protein are converted to fat. The body can make saturated and monounsaturated fatty acids by modifying other fatty acids or by de novo synthesis from carbohydrate and protein. However, certain polyunsaturated fatty acids, such as linoleic acid, cannot be made by the body and must be supplied in the diet. Fat is mobilized from adipose tissue into the blood as free fatty acids. These form a complex with blood proteins and are distributed throughout the organism. The oxidation of free fatty acids is a major source of energy for the body. The predominant dietary fats (i.e., over 10 carbons long) are of relatively equal caloric value. The establishment of the common pathway for the metabolic oxidation and the energy derived, regardless of whether a fatty acid is saturated, monounsaturated, or polyunsaturated and whether the double bonds are cis or trans, explains this equivalence in caloric value. C. Essential Fatty Acids Experimental work in the 1930’s in animals and humans demonstrated that certain long chain polyunsaturated fatty acids, linoleic and arachidonic, are essential for growth and good skin and hair quality. Now linoleic and linolenic acids are termed “essential” because they cannot be synthesized by the body and must be supplied in the diet. Arachidonic acid, however, can be synthesized by the body from dietary linoleic acid. Arachidonic acid is considered an essential fatty acid because it is an essential component of membranes and a precursor of a group of hormone-like compounds called eicosanoids including prostaglandins, thromboxanes, and prostacyclins which are important in the regulation of widely diverse physiological processes. Linolenic acid is also a precursor of a special group of prostaglandins. The dietary fatty acids that can function as essential fatty acids must have a particular chemical structure, namely, double bonds in the cis configuration and in specific positions (carbons 9 and 12 or 9, 12, and 15 from the carboxyl carbon atom or carbons 6 and 9 or 3, 6 and 9 from the methyl end of the molecule) on the carbon chain. The requirement for these essential fatty acids has been demonstrated clearly in infants. While the

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minimum requirement has not been determined for adults, there is no doubt that they are essential nutrients. The current American diet provides at least the minimum essential fatty acid requirement. According to the Food and Nutrition Board’s Recommended Dietary Allowances (2), the amount of dietary linoleic acid necessary to prevent essential fatty acid deficiency in several animal species and also in humans is 1 to 2% of dietary calories. However, for much of the general population, 3% of calories as linoleic acid is considered to be a more satisfactory minimum intake. In the case of linolenic acid, the requirement for humans has been estimated to be 0.5% of calories. The Committee on Diet and Health of the Food and Nutrition Board (3) has recommended that the average population intake of polyunsaturated fatty acids (primarily linoleic acid) remain at the current level of about 7% of calories and that individual intakes not exceed 10% of calories because of lack of information about the long-term consequences of a higher intake. For many reasons, especially because essential fatty acid deficiency has been observed exclusively in patients with medical problems affecting fat intake or absorption, the Food and Nutrition Board has not established an RDA for omega-3 or omega-6 polyunsaturated fatty acids. D. Fat Level in the Diet Fats in the diet are often referred to as “visible” or “invisible.” Visible fats are those added to the diet in foods such as salad dressings, spreads and processed foods, whereas invisible fats are those that are naturally occurring in foods such as meats and dairy products.

According to the Economic Research Service of USDA, between 1970 and 1997, Americans increased their consumption of total visible fat from 52.6 to 65.6 pounds per person per year (see Table X). On the other hand, if these data are expressed as a percentage of total calories consumed, fat intake from visible and invisible sources would appear to have decreased from about 43% to about 33% of calories. This apparent paradox of increasing amounts of fat consumed per day while decreasing the percentage of fat calories is explained by the fact that while daily fat consumption has been increasing recently, total caloric intake has been increasing at a greater rate (4). This increased level of calorie intake will reduce the calculated percentage of calories from fat even though actual fat consumption has not gone down. The dietary trend of increased caloric consumption is thought to be the result of increased carbohydrate intake, larger food portions being

consumed, more eating occasions, and increased soft drink and alcoholic beverage intake (4).

Fat intake is generally measured by two methods: (1) surveys of individuals recalling the amounts of foods consumed over a specific time period and (2) “consumption” estimates from food disappearance data as calculated from available sources. The latter method may overstate actual consumption estimates because food disappearance data do not account for foods wasted or discarded and lost to spoilage, trimming, or cooking. It has been estimated that wastage of deep frying fats used in the food service sector may be as high as 50% (5); therefore, food component estimates from food “disappearance” data, particularly fat, may be overestimated. The accuracy of dietary recall data is also difficult to ensure due to errors of memory in recalling foods eaten previously.

Dietary guidelines were first issued by the American Heart Association in the early 1970s in an attempt to educate Americans as to the importance of a healthful diet. The U.S. Department of Agriculture in conjunction with the U.S. Department of Health and Human Services later developed Dietary Guidelines for Americans in 1980. In 1990 these guidelines first included recommended limitations for fat consumption which remained unchanged in a 1995 update (6) of the guidelines. The guidelines for fat call for a total fat intake of no more than 30% of calories with a saturated fatty acid intake of no more than 10% of calories. Although these dietary guidelines for fat have been established for over 20 years, the relatively small changes in fat intake during this time period reflect the difficulty on a national scale in achieving dietary goals such as reducing fat intake. E. Diet and Cardiovascular Disease Cardiovascular diseases, which include heart attack and stroke, are the leading causes of death in the United States. The most predominant form of cardiovascular disease is coronary heart disease or CHD (commonly referred to as “heart attack”) which, according to the American Heart Association (AHA), is the single leading cause of death in America resulting in 481,287 deaths in 1995 (7). Atherosclerosis, the gradual blocking of arteries with deposits of lipids, smooth muscle cells, and connective tissue, contributes to most deaths from cardiovascular disease. Cardiovascular diseases are chronic degenerative diseases of complex etiology that often are associated with aging. A number of risk factors for cardiovascular disease have been identified from epidemiological studies. These include positive family

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history of cardiovascular disease, cigarette smoking, hypertension (high blood pressure), elevated serum cholesterol, obesity, diabetes, physical inactivity, male sex, age, and excessive stress. Although these risk factors have been associated statistically with the incidence and mortality of cardiovascular disease, no cause and effect relationships have been established. During the 1950s considerable interest began to develop concerning a possible relationship between dietary fat and the incidence of coronary heart disease. This interest has continued to the present time. Since diet can affect serum cholesterol and since heart attack risk increases with increasing serum cholesterol levels, some health advisory organizations (e.g., the American Heart Association, Office of the Surgeon General, the National Institutes of Health, and the National Academy of Sciences) have recommended diet modification to achieve lower serum cholesterol levels in the general population. These diet modifications include reducing consumption of total fat, saturated fat, and cholesterol. Researchers now recognize that total serum cholesterol is distributed largely between two general classes of lipoprotein carriers, low-density lipoprotein (LDL) and high-density lipoprotein (HDL). The largest portion of total cholesterol is in the LDL fraction, and elevated levels of LDL cholesterol are associated with increased coronary heart disease risk. On the other hand, high levels of HDL cholesterol have been associated with protection against coronary heart disease. One factor that has been related to increased levels of HDL cholesterol is regular exercise. However, it is uncertain whether diet or exercise related modifications of LDL or HDL levels will affect development of coronary heart disease. Long-term studies are currently in progress to address these questions. The National Cholesterol Education Program (NCEP) was established in the mid-1980s by the National Heart, Lung, and Blood Institute, National Institutes of Health, to increase public and health professional awareness regarding the importance of lowering elevated serum cholesterol levels. In 1987 guidelines were established by the Adult Treatment Panel, which embodied two approaches for a coordinated strategy for reducing coronary risk (8). The first is a “population” approach, which attempts to lower serum cholesterol levels of the entire U.S. population through dietary change. The second approach attempts to identify individuals at high risk of developing heart disease and to provide them with diet and/or drug therapy. In 1993, a second Adult Treatment Panel updated the earlier guidelines and recommendations for cholesterol management (9). The panel’s

recommendations were very similar to previous guidelines. The panel confirmed that low-density lipoprotein (LDL) cholesterol should continue to be the primary target of cholesterol lowering efforts. The most significant of the few additional recommendations included adding age (>45 years in men and >55 years in women) as a risk factor for CHD. The American Academy of Pediatrics (AAP) in concert with the NCEP guidelines endorses selective cholesterol screening of children older than two years of age whose parents have a history of CHD (10). However, the AAP does not recommend restrictions in fat intake in children younger than two years of age. The levels of total cholesterol and the LDL and HDL fractions in the blood are influenced by a combination of factors, including age, sex, genetics, diet, and physical activity. Diet and exercise are factors which individuals can modify and thus have been a basis for recommendations to reduce risk factors for chronic diseases such as coronary heart disease. The three major categories of dietary fatty acids (saturated, monounsaturated, and polyunsaturated) appear to influence total, LDL, and HDL cholesterol in different ways. Predictive equations have been developed and applied. In general, diets high in saturated fatty acids increase total as well as LDL and HDL cholesterol levels compared to diets low in saturated fatty acids. The specific saturated fatty acids palmitic (the principal saturated fatty acid in the U.S. diet), myristic and lauric acids are considered to be cholesterol raising, whereas stearic acid and medium-chain saturated fatty acids (6 to 10 carbon atoms) have been considered to be neutral with respect to effects on blood lipids and lipoproteins.

Monounsaturated (e.g., olive, canola) and polyunsaturated (e.g., sunflower, corn, soybean) fatty acids are cholesterol lowering when they replace significant levels of saturated fatty acids in the diet. Clinical and epidemiological studies indicate that polyunsaturates lower LDL and total cholesterol. Some studies have found that diets high in monounsaturated fatty acids compared with polyunsaturated fatty acids decrease LDL cholesterol while maintaining HDL cholesterol levels (11,12). Other work has suggested that the effect of consuming polyunsaturated fat and monounsaturated fat is similar and results in a decrease in both LDL and HDL cholesterol (13). There is currently disagreement among health authorities on whether unsaturated fatty acids in the American diet should be reduced in favor of complex carbohydrates. Studies have shown that dietary components other than fats and oils, including proteins, carbohydrates, fiber and trace minerals, may also affect blood lipid levels and the development of

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atherosclerosis. Thus, a possible relationship between diet (particularly fats) and coronary heart disease remains uncertain, and the appropriateness of specific dietary recommendations for the general population is not agreed upon. Additional research will be necessary to clarify the uncertainties. In the meantime, nutritionists emphasize moderation in the consumption of fat as well as other nutrients. While atherosclerosis is the slow, progressive narrowing of an artery that gradually reduces blood flow, the actual precipitating event of a heart attack is frequently thrombosis, the formation of a blood clot that can lodge in an artery blocking blood flow. If the blockage of the artery is complete, a heart attack or stroke may result. There is current scientific interest in whether atherosclerosis (including elevated serum cholesterol levels) is related to thrombotic risk. With regard to how specific dietary fatty acids might affect thrombotic tendency, it has been demonstrated that polyunsaturated omega-3 fatty acids (e.g., from fish oils) have antithrombotic effects. The mechanisms of these effects appear to involve the metabolism of compounds related to eicosanoids. In contrast to the effects of polyunsaturated omega-3 fatty acids, there appears to be no direct evidence that dietary long-chain saturated fatty acids, such as stearic acid, are thrombogenic to humans. Although some epidemiological evidence suggests that saturated fatty acids may play a role in thrombotic events, more research is needed to establish whether there is a relationship to thrombotic risk and to elucidate the possible mechanism of action. Lipoprotein(a), or Lp(a), a particle similar to low density lipoprotein (LDL), has been suggested by some researchers to be a risk factor for CHD due to its high serum levels in many heart attack victims who otherwise have no obvious risk factors. Lp(a) levels are thought to be largely controlled by genetic factors, however, some reports indicate that the diet also may influence Lp(a) levels (14, 15). Recent research has revealed that LDL particle size may influence one’s susceptibility to CHD (16). Specifically, an abundance of smaller size LDL particles has been associated with increased CHD risk. It has been determined that approximately 67% of men and 80% of women in the U.S. have a high proportion of LDL particles whose size is relatively large (approximately 270 angstroms in diameter). The remaining population has LDL particles that are somewhat smaller (approximately 250 angstroms in diameter). The larger LDL is characterized as Phenotype A and the smaller LDL as Phenotype B. Phenotype B has been shown to be particularly atherogenic and is associated with lower HDL levels, higher triglycerides, higher levels of

intermediate density lipoproteins, and an increased risk of CHD. Although LDL Phenotypes A and B are thought to be determined by genetics only, some recent work suggests that substantial reductions in energy from fat could be detrimental to certain individuals. The American Heart Association (AHA) has taken the position that dietary factors influence the risk of CHD (17). The AHA believes the three most important dietary risk factors for atherogenesis are saturated fat, cholesterol, and obesity. The AHA has established a two-step dietary guidance program designed to reduce total fat, saturated fat and cholesterol, which it believes could reduce average blood cholesterol levels in the U.S. by 5-15%. The AHA encourages carbohydrate intake be increased to replace those calories lost through reductions in fat intake. A trend of considerable interest to epidemiologists and other health professionals is the continuing decline in the death rate from cardiovascular diseases. During the period 1984 to 1994, the U.S. age-adjusted death rate from cardiovascular diseases (considered as a whole) decreased about 22% (7). In particular, the mortality from coronary heart disease decreased 29% during this period (7). Specific reasons for decreasing mortality due to cardiovascular disease are not known. However, recognition and increased public awareness of major risk factors (cigarette smoking, hypertension, and elevated serum cholesterol) and more effective treatment of heart disease have probably played roles. The decline in heart disease mortality in the U.S. has been observed in all decades of life, in all races, and in both sexes. F. Diet and Cancer

Cancer is the second leading cause of death in the United States, exceeded only by heart disease. The American Cancer Society predicted that about 564,800 Americans would die of cancer in 1998 (18). The three most common sites of fatal cancer in men are lung, prostate, and colo-rectal. In women, the three most common sites are lung, breast, and colo-rectal. In men and women, cancers at these top three sites account for about half of all cancer fatalities.

Cancer is a group of diseases characterized by uncontrolled growth and spread of abnormal cells. If the spread is not controlled, it can result in death. Cancer is caused by both external factors (e.g., chemicals, radiation, and viruses) and internal factors (e.g., immune conditions and inherited mutations). Causal factors may act together or sequentially to initiate or promote carcinogenesis. Frequently the time period between exposures or mutations and appearance of cancer is very

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long, often 10 years or longer. Risk factors contributing to cancer development include cigarette smoking, certain dietary patterns, exposure to sunlight, exposure to radioactive materials or specific chemicals, and family history. All cancers caused by cigarette smoking and heavy use of alcohol are considered preventable. Many cancers related to dietary factors or to sunlight exposure are also felt to be preventable. Unlike heart disease in which blood cholesterol levels serve as an indictor of risk, there are no similar types of markers to indicate a cancer may be developing. Early detection of cancer, for instance through regular screening examinations, greatly increases the chances of successful treatment.

According to the American Cancer Society (18), between 1991 and 1995, the national cancer death rate fell 2.6%. Most of the decline was attributed to decreases in mortality from cancers of the lung, colon-rectum, and prostate in men, and breast, colon-rectum, and gynecologic sites in women. The declines in mortality were greater in men than in women, largely because of changes in lung cancer rates; greater in young patients than in older patients; and greater in African-Americans that in Caucasians, although mortality rates remain higher in African-Americans.

Some scientific studies have reported associations between dietary factors, such as low intake of dietary fiber or high intake of fat, and the appearance of cancer at certain sites. Such studies are called epidemiological studies. They assess the existence of relationships between factors, such as diet and development of diseases like cancer. These studies do not prove cause and effect. For example, incidence of breast and colon cancer have been correlated with variations in diet, especially fat intake. However, a causal role for dietary factors has not been firmly established. A recent study of approximately 90,000 women in the U.S. found no significant association between diets high in fat and breast cancer (19). Also in developed countries, certain types of cancer may be related more closely to excessive calorie intake than to any specific nutrient. Overall, there is no evidence of a causal relationship between macronutrients in the diet and cancer.

Laboratory animal studies on diet and cancer have dealt largely with the response of chemically-induced or transplanted tumors to increased calories from extra fat in the diet. Some of these studies have suggested that dietary calories and type of fat consumed may be related to cancer incidence, particularly with breast and colon cancer. Other animal studies have indicated that moderate caloric restriction may result in lower cancer incidence and, for a given level of fat in the diet, animals may develop a higher incidence of cancer

when the fat is unsaturated. Some studies suggest that a high level of dietary fat may act as a promoter of carcinogenesis rather than as an initiator of tumors. A promoter is a compound that by itself is not carcinogenic but which enhances the ability of a carcinogen to produce cancer. The existence, however, of a direct relationship between caloric content, fat unsaturation, and carcinogenesis is still unclear.

In addition to interest in effects of the total amount of fat in the diet, there is also interest in whether individual types of fatty acids can affect cancer risk. A recent assessment of currently available data suggests that specific saturated, monounsaturated, or polyunsaturated fatty acids do not affect cancer risk (20). Although animal studies have suggested that polyunsaturated fatty acids may increase tumor growth, no relationship has been found between polyunsaturated fatty acids and cancer in humans (21). Similarly, studies in animals have found that omega-3 fatty acids (e.g., from fish oils) suppress cancer formation, but at this time there is no direct evidence for protective effects in humans. Oleic acid and saturated fatty acids have not been found to have any specific effects on carcinogenesis. Available scientific evidence also does not support a relationship between trans fatty acids and risk of cancer at any of the major cancer sites. On a positive note, recent studies have shown that conjugated linoleic acid, found primarily in lipids from ruminant animals, appears to be unique among fatty acids because low levels in the diet produce significant cancer protection. This effect seems to be independent of other dietary fatty acids. (For further discussion of conjugated linoleic acid, see section H, Areas of Current Research Interest.)

Accumulating evidence suggests that diets rich in antioxidant vitamins (in particular, vitamins A and C) may help reduce the risk of some cancers. Vitamins A and C are abundant in many fruits and vegetables. Vitamin E is an antioxidant vitamin found principally in vegetable oil products. There is less epidemiological evidence regarding vitamin E, however, laboratory and animal data support its anticarcinogenic activity. Further research is needed to establish dietary levels of antioxidants that are both safe and effective.

The American Cancer Society has suggested (18) from existing scientific evidence that about one-third of the cancer deaths that occur in the U.S. each year are due to dietary factors. Another third is due to cigarette smoking. Thus, for the majority of Americans who do not use tobacco, dietary choices and physical activity become important modifiable determinants of cancer risk. Evidence also indicates that although genetics are a factor in the development of cancer,

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heredity does not explain all cancer occurrences. Behavioral factors such as tobacco use, dietary choices, and physical activity modify the risk of cancer at all stages of its development. Adopting healthful diet and exercise practices at any stage of life can promote health and likely reduce cancer risk.

Many dietary factors can affect cancer risk: types of foods, food preparation methods, portion sizes, food variety, and overall caloric balance. The American Cancer Society believes that cancer risk can be reduced by an overall dietary pattern that includes a high proportion of plant foods (fruits, vegetables, grains, and beans), limited amounts of meat, dairy products, and other high-fat foods, and a balance of caloric intake and physical activity. Plant foods contain fiber, which is believed to reduce the risk of cancers of the rectum and colon. They also are rich in antioxidant vitamins, minerals, and phytochemicals that may play a role in reducing cancer risk.

Overall, in the area of diet and cancer, a significant challenge is relating promising data from animal and cell culture studies to the prevention of cancer in humans. G. Health Effects of Trans Fatty Acids from

Hydrogenation Hydrogenation is the process of chemically adding hydrogen gas to a liquid fat in the presence of a catalyst. This process converts some of the double bonds of unsaturated fatty acids in the fat molecules to single bonds, thereby increasing the degree of saturation of the fat. The degree of hydrogenation, that is, the total number of double bonds which are converted, determines the physical and chemical properties of the hydrogenated oil or fat. An oil that has been “partially” hydrogenated often retains a significant degree of unsaturation (i.e., double bonds) in its fatty acids. Hydrogenation also results in the conversion of some cis double bonds to the trans configuration (see Part IV, Section C, Isomerism of Unsaturated Fatty Acids) and in the formation of cis or trans positional isomers in which one or more double bonds has migrated to a new position in the fatty acid chain. The levels and types of these isomeric fatty acids formed depend on the type of oil and conditions (e.g., temperature, pressure, catalyst, and duration) of the hydrogenation processing. Small amounts of trans fatty acids occur naturally in foods such as milk, butter, cheese, beef, and tallow as a result of biohydrogenation in ruminants. USDA has estimated that up to 20% of the trans fatty acids in the American diet are from ruminant sources (22). Traces of trans isomers may also be formed when

nonhydrogenated oils are deodorized under certain conditions (e.g., prolonged heating at high temperatures). The hydrogenation process is very important to the food industry to achieve desired stability and physical properties in such food products as margarines, shortenings, frying fats, and specialty fats. Examples of enhanced stability provided by hydrogenation include increased shelf life of commercial snack foods and prolonged frying stability of food service deep frying fats. An example of a desired physical property is the semi-solid consistency at refrigerator and room temperatures of margarines and spreads. Trans isomers were a principal objective in solid shortening and margarine products of the 1950s and 1960s because of their ability to contribute higher melting properties while maintaining an unsaturated character. More recent concerns about trans isomers acting physiologically like saturated fatty acids has encouraged the industry to pursue reduced levels of trans isomers in many food products. Current partially hydrogenated restaurant and food service frying oils typically contain about 10-35% trans isomers. Tub margarines and spreads (on a product basis) typically contain trans fatty acid levels up to 16%, whereas stick margarines typically have trans fatty acid levels around 15-22%. Widespread use of partially hydrogenated vegetable oils in the U.S. during the past six or seven decades has raised questions about possible adverse consequences of consuming the isomeric fatty acids present in these products. The principal isomeric fatty acids of interest have been trans fatty acids rather than positional isomers of cis fatty acids. Studies concerning health effects of trans fatty acids have focused primarily on their levels in the U.S. diet and their effects on parameters related to coronary heart disease risk. The Institute of Shortening and Edible Oils (ISEO) has reported an estimate of trans fatty acids available for consumption in the U.S. diet for 1989 to be about 8 g/person/day (22). This estimate is considered to be relevant to the present day because few changes have occurred in the U.S. diet since around 1989 that would have modified appreciably the estimate. The ISEO’s estimate was based on a comprehensive analysis of products made from partially hydrogenated fats and oils that were available for consumption. Availability estimates do not represent actual consumption but rather indicate what could be consumed on average. Using data from the USDA’s Continuing Survey of Food Intakes by Individuals, Allison, et al (23) estimated the mean intake of trans fatty acids by the U.S. population to be 5.3 g/day, which is substantially lower than the ISEO’s

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availability estimate of 8 g/person/day. Estimates of trans fatty acid levels in the U.S. diet by various investigators have indicated that trans acids contribute only about 2 to 4% of total energy. This is a small percentage compared to saturated fatty acids, which contribute 12-14% of energy intake (24, 25). A major study involving 14 Western European countries was conducted by the TNO Institute of the Netherlands assessing trans fatty acid intake using compositional data developed during the study and available national food consumption data (26). Trans fatty acid intake ranged from 1.2 g/d in Portugal to 6.7 g/d in Iceland. The overall mean of trans fatty acid intake was 2.4 g/d, smaller than expected by the investigators. Prior to 1990, there were numerous reviews and studies on the nutritional and biological effects of trans fatty acids. Most of these studies focus on the development of atherosclerosis and on the effects of trans fatty acids on serum cholesterol levels. Generally these studies indicated that trans fatty acids were not uniquely atherogenic nor did they raise total cholesterol compared to cis fatty acids. However, these findings were challenged in 1990 by a Dutch study (27) which indicated that a diet high in trans fatty acids (11.0% energy) raised total and LDL cholesterol and lowered HDL cholesterol in human subjects compared to a high oleic acid diet. A follow-up study by these investigators using a somewhat lower level of dietary trans fatty acids (7.7% energy) reported that dietary trans acids raised total and LDL cholesterol and lowered HDL cholesterol compared to a high linoleic acid diet but not compared to a high stearic acid diet. The results of these studies stimulated a major U.S. clinical trial which examined the health effects of both high (6.6% energy) and moderate (3.8% energy) levels of trans acids compared with high oleic acid (16.7% energy) and high saturated fatty acid (16.2% energy as lauric, myristic and palmitic acids) levels (28). The results were that the high and moderate trans fatty acid diets increased total and LDL cholesterol compared to the oleic acid diet but reduced total and LDL cholesterol compared to the high saturated fatty acid diet. The high trans diet, but not the moderate trans diet resulted in a minor reduction in HDL cholesterol. Lp(a) levels were not affected by the trans diets compared to the oleic diet when all subjects were considered collectively (29). Judd, et al, (30) have conducted a follow-up study to address limitations noted in previous studies. A high carbohydrate diet was included as a control to assess if direct addition of trans fatty acids to the diet has an independent cholesterol raising effect. Other

dietary treatments included high oleic acid, high stearic acid, high trans, moderate trans, and high saturated fatty acids. Compared to the control diet, the trans fatty acid diets raised total and LDL cholesterol to about the same extent as the high saturated diet but they had no effect on HDL cholesterol. The stearic acid diet had no effect on LDL cholesterol but lowered HDL cholesterol. Most of the studies on health effects of trans fatty acids conducted during the 1970s and 1980s found no significant associations between trans fatty acid intake and risk of coronary heart disease. On the other hand, recent epidemiological studies have reported that trans fatty acids have a positive association with CHD risk (31). There are a number of limitations of these studies including the difficulty of measuring trans fatty acid intake through the use of food frequency intake questionnaires, the lack of a dose response relationship between trans fatty acid intake and heart attack risk and the inconsistency of study results. Above all it must be remembered that epidemiological studies do not show cause and effect and are simply indicators of where clinical studies may be needed. Furthermore, the mortality from CHD in the U.S. has continued to decrease during the past 25-30 years (32), a period in which the availability for consumption of trans fatty acids has remained relatively constant (22). Scientists have also performed numerous studies using animal models to investigate the health effects of trans fatty acids. Available data from short-term studies involving rabbits, hamsters, pigs, and monkeys have demonstrated that trans fatty acids in the presence of adequate essential fatty acids did not produce atherosclerosis. Four recent comprehensive reports have addressed possible health effects of trans fatty acids. A British Nutrition Foundation Task Force (33) concluded that “the risk attributable to the current low intake of trans fatty acids (4-6 g/person/day) which accounts for 2% of dietary energy in the UK appears to be small, although extreme consumers may experience higher risk.” A report by the International Life Sciences Institute (ILSI) (24) emphasized that since trans fatty acids are often substituted for unsaturated fatty acids in experimental diets, it is unclear whether the responses reported reflect the addition of trans fatty acids to the diets or the reduction in dietary unsaturated (i.e., cholesterol-lowering) fatty acids. Another ILSI report (34) addressed whether dietary trans fatty acids compromise fetal and infant early development. The report concluded that there is little evidence in animals or humans that trans fatty acids influence growth, reproduction, or gross aspects of fetal development. An ASCN/AIN Task Force on Trans Fatty acids (25)

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concluded that “compared to saturated fatty acids, the issue of trans fatty acids is less significant because the U.S. diet provides a smaller proportion of trans fatty acids and the data on their biological effects are limited.” The Task Force recommended that data be obtained on the intake of trans fatty acids, their biological effects, mechanism of action, and relation to disease that are comparable to those for saturated fatty acids. In contrast to the amount of literature on trans fatty acids in relation to coronary heart disease, relatively few investigators have studied trans fatty acids with respect to cancer. Ip and Marshall (35) published a comprehensive review of more than 30 reports addressing this issue. With respect to breast cancer, Ip and Marshall noted that epidemiologic evidence shows only slight to negligible impact of fat intake in general on breast cancer risk and no strong evidence that intake of trans fatty acids is related to increased risk. In addition, there is no evidence indicating that intake of trans fatty acids is related to increased risk of either colon cancer or prostate cancer. Overall, the available scientific evidence does not support a relationship between trans fatty acids and risk of cancer at any of the major cancer sites. In summary, recent comprehensive reviews of the literature indicate that trans fatty acids at their current level of intake are a safe component of the diet. At relatively high levels of intake, trans fatty acids appear to raise LDL and lower HDL cholesterol. When substituted for unhydrogenated oils high in unsaturated fatty acids, trans fats increase total and LDL cholesterol. However, trans fats lower total and LDL cholesterol when substituted for animal fats and vegetable oils high in saturated fatty acids. Hydrogenated oils are used mainly as a substitute for more highly saturated vegetable oils and for animal fats containing both saturated fatty acids and cholesterol. Since trans fatty acids appear to raise total and LDL cholesterol levels to about the same extent as saturates but are present in the U.S. diet at a much lower level compared to saturates (2-4% versus 12-14% of energy), they pose less of a health concern than do saturated fatty acids. Consumers lowering their fat intake to 30 percent of calories, as recommended in the U.S. Dietary Guidelines for Healthy Americans (6), will simultaneously reduce their intake of saturated as well as trans fatty acids. H. Areas of Current Research Interest

A group of isomers of the essential fatty acid linoleic acid, collectively termed “conjugated linoleic acid” (CLA), has received considerable attention in recent years because these isomers appear to have both

anticarcinogenic and antiatherogenic properties and may affect body composition. CLA differs from linoleic acid by the position and geometric configuration of one of its double bonds. CLA isomers are found primarily in lipids originating from ruminant animals (beef, dairy, and lamb) and are reported to range from about 3 to 11 mg/g fat (36). Fats from nonruminants (pork and chicken) and vegetable oils contain lower amounts of CLA ranging from 0.6 to 0.9 mg/g fat (37). The availability for consumption of CLA in the U.S. has been estimated to be on the order of several hundred milligrams per day (38).

Animal studies have indicated that CLA reduces the incidence of tumors induced by carcinogens such as dimethylbenz[a]anthracene and benzo[a]pyrene (39-45). CLA appears to be a unique anticarcinogen because it is a naturally occurring substance found primarily in food products derived from animal sources. Most other naturally occurring substances that have been demonstrated to have anticarcinogenic activity are of plant origin. CLA is also unique because it is a fatty acid mixture and anticancer efficacy is expressed at concentrations close to human consumption levels. Inhibition of tumor development in animals has been seen with CLA at concentrations as low as 0.1% in the diet.

In addition to its anticarcinogenic properties, CLA appears to be antiatherogenic as well. Recent studies involving rabbits (46) or hamsters (47) indicated that incorporation of CLA into the diets suppressed total and LDL-cholesterol and also atherosclerosis. Furthermore, dietary CLA is able to affect body composition (48, 49). Diets supplemented with 0.5% CLA have been found to decrease body fat content and increase lean body mass in several species including poultry, pigs, and rodents. Pigs fed CLA also showed improved feed efficiency (weight gain per unit weight of food consumed) and improved immune systems compared to controls. Thus, in the future CLA could be a useful additive for animal feeds. Further research is needed to elucidate the mechanism of CLA to inhibit cancer and atherosclerosis. Human studies on body composition effects are underway at this time.

Another area of recent research interest is in the possibility of using dietary intake of certain plant sterols, such as sitosterol, to help reduce the risk of coronary heart disease. Sitosterols were found to be serum cholesterol lowering agents in the 1950s, and their mode of action appeared to be due to the inhibition of cholesterol absorption during the digestive process (50). Recent studies with humans have examined the serum cholesterol lowering ability of sterol esters incorporated into margarines. A Finnish study utilized

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sitostanol esters, a hydrogenated sitosterol obtained from a wood pulp byproduct, fed in margarine to mildly hypercholesterolemic subjects at levels ranging from 1.9-2.6 g sitostanol/day. A mean reduction in plasma serum cholesterol of 10% was observed after one year (51). A second study used esters of sitosterol that were extracted from soybean oil and incorporated into margarine, and compared their cholesterol lowering effect directly with that of sitostanol esters. This study, using normocholesterolemic and mildly hypercholesterolemic subjects, found a reduction of 8-13% of plasma total and LDL cholesterol levels, and both the soybean sterols and the sitostanols were equally effective compared to the control diet (52). In 1995, a margarine containing sitostanol esters from wood pulp was introduced commercially in Finland. The product proved to be very popular and initially demand outstripped supply. This success has stimulated proposals to launch the product in the U.S. in 1999. At the same time, a commercial margarine containing sitosterol esters obtained from soybean oil has been developed for the U.S. and European markets. Both the sitosterol based and sitostanol based margarines are expected to be introduced in the U.S. in mid-1999, pending regulatory approval. I. Nonallergenicity of Edible Oils Food allergies are caused by the protein components of food. Edible oils in the U.S. undergo extensive processing (sometimes referred to as “fully refined”, discussed in section VII Processing) which removes virtually all protein from the oil. Refined edible oils therefore do not cause allergic reactions because they do not contain allergenic protein. Food products containing refined edible oils as ingredients are also non-allergenic unless the food products contain other sources of protein.

Some edible oils may be extracted and processed by procedures that do not remove all protein present. While the vast majority of oils found in the US are refined by processes which remove virtually all protein, mechanical or “cold press” extraction is occasionally used, which may not remove all protein. These cold pressed oils are rarely used domestically and are usually found only in health food or gourmet food stores. Studies using cold pressed soybean oil have shown it to be safe; however, insufficient testing has been done to ensure that all cold pressed oils can be safely consumed by sensitive individuals. Edible oils have been blamed for causing allergic reactions in people, but there are conflicting views and inadequate scientific evidence regarding their

allergenicity. Many reports alleging edible oil allergenicity have been testimonial in nature. Of those reports that have been scientifically recorded, most lack evidence that edible oils were indeed the causative agent or were even ingested. For example, many investigators did not perform tests to confirm an allergic response from the oil in question nor were analyses conducted to determine if protein was present in the oil. Also many reports do not indicate if the oils were cold pressed or not. There is also a lack of scientific data to determine the levels of proteins needed to cause an allergic reaction; therefore such tolerance levels in humans have not been established. Furthermore, the sensitivities of food allergic individuals may vary widely, and not all allergenic foods have the same tolerance level. While some consumers are convinced they are allergic to edible oils, there are usually alternate explanations for these reactions. For example, foods containing peanuts, a common allergenic food ingredient, may be cooked in peanut oil. An allergic reaction experienced as a result of eating this food may be mistakenly blamed on the oil. Also foods containing inherent allergens may be cooked in edible oils resulting in traces of the allergenic protein being left behind in the oil. Restaurants and food service facilities should therefore exercise caution in cooking techniques and be able to readily identify not only the oils used but also a complete list of all foods cooked in the oil. The vast preponderance of edible oils consumed in the US are highly refined and processed to the extent that allergenic proteins are not present in detectable amounts. The majority of well-designed and performed scientific studies indicate that refined oils are safe for the food-allergic population to consume (53). J. Biotechnology Biotechnology has been defined broadly as the commercial application of biological processes. It includes both hybridization and genetic modification of plants and animals. The goal of biotechnology is to develop new or modified plants or animals with desirable characteristics. The earliest applications of this technology have been in the pharmaceutical, cosmetic and agricultural sectors. Agricultural applications to food crops have resulted in improved “input” agronomic traits, which affect how the plants grow. Such traits include higher production yields, altered maturation periods, and resistance to disease, insects, stressful weather conditions, and herbicides. Currently researchers and seed developers are placing more emphasis on improving “output” quality traits which affect what the plant produces. An example of this

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application is the custom designing of nutrient profiles of food crops for improved nutrition and reduced allergenic properties. The more notable biotechnology applications within the oilseed industry include herbicide tolerant soybeans and canola, high and midoleic sunflower, low linolenic/low saturate soybeans, high linoleic flaxseed oil, low linolenic canola, high laurate canola, high oleic canola, and high stearate canola. Exciting opportunities for edible oil crop nutrient content and functionality improvement include reduction in saturated fatty acid content, improved oxidative stability resulting in a reduced need for hydrogenation, reduced calories or bioavailability, creation of specific fatty acid profiles for particular food applications, and creative “functional” foods for the population at large or for medical purposes. Other applications may include increased oil yield, improved extraction of oil from oilseeds through enzyme technology, industrial production of fatty acids, and improved processing methods. Genetic engineering is a specific application of biotechnology. This technique is also called recombinant DNA technology, gene splicing, or genetic modification, and involves removing, modifying, or adding genes to a living organism. New plant varieties that result from genetic engineering are referred to as transgenic plants. The most recognized examples in the U.S. are herbicide resistant soybeans, corn which is resistant to the European corn borer, and cotton which is resistant to the bollworm. The acceptance and utilization of these and other transgenic food crops in the U.S. have been very rapid. For example, transgenic herbicide resistant soybeans after being first introduced commercially in 1996 on 1 million acres were planted on about 25 million acres in 1998. Genetically modified insect resistant corn was also commercially introduced in 1996, and it occupied about 16 million acres in 1998. Transgenic soybeans and corn are expected to be about 50% of the U.S. total planted acreage for these crops in 1999. Global plantings of transgenic crops are also increasing at very rapid rates. While almost 7 million acres were planted internationally to transgenic crops in 1996, about 31.5 million acres were planted in 1997 (54). All indications are that worldwide acreage will continue to expand at a rapid pace for the next several years. The most popular crops as a percent of total global acreage planted to transgenic crops are the following: soybeans (40%), corn (25%), tobacco (13%), cotton (11%), and canola (10%). The United States is the leader in agricultural applications of genetically engineered crops representing 64% of the total global acreage devoted to transgenic crops in 1997, followed by

China with 14%, Argentina with 11%, Canada with 10% and Australia and Mexico with about 1% each (54). In the U.S., the Food and Drug Administration has principal regulatory responsibility for approving the introduction of foods and food additives from transgenic plants into the marketplace. The agency has maintained a biotechnology policy since 1992, which states that foods derived from new genetically engineered plant varieties will be regulated essentially the same as foods created by conventional means. Labeling of such foods or food additives is not required unless the nutrient composition is significantly altered, allergenic proteins have been introduced into the new food, or unique issues have been posed which should be communicated to consumers. While U.S. consumers appear to have accepted biotechnology and recognize its potential benefits (e.g., foods, drugs), Europeans have been less willing to embrace biotechnology due to concerns regarding the safety of genetically modified foods. The European Union requires foods containing genetically altered components to be labeled as such and has been very slow in approving new genetically modified plant varieties as imports. This position has caused much anxiety between Europe and the U.S. from an agricultural trade standpoint. The prospects for resolution of these differences between Europe and the U.S. appear to be improving. As new varieties of oilseeds are developed to incorporate specific fatty acid components, historical fatty acid profiles for source oil identification will become less useful. A challenge for food manufacturers will be how to identify these food components through food labeling. The age of biotechnology is here with a vast array of improved plant varieties already commercially available. The future looks bright particularly for the emergence of new oilseed varieties that will have improved agronomic characteristics, nutrient profiles, and functionality in foods and food ingredients as well as in industrial products. It is therefore important for consumers to understand the many benefits of biotechnology and that the application of genetic engineering technology to foods will render them safe, more functional, and nutritious. K. Fat Reduction in Foods Americans have been advised during the past two decades by many health organizations, including the Office of the Surgeon General, American Heart Association, U.S. Department of Agriculture, and Department of Health and Human Services, to reduce total dietary fat intake to less than 30% of calories and

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saturated fat intake to less than 10% of calories. High intake of total and saturated fat has been associated with increased risk of obesity and coronary heart disease. Healthy People 2000, a program of the U.S. Public Health Service to promote health and prevention of disease, recommended food manufacturers double the availability of lower fat food products from 1990 to the year 2000. That goal was quickly met by 1995. One of the primary methods employed by the food industry in creating newer food products containing less fat has been the use of fat replacers or fat substitutes. The technology used in the development of these fat replacers allows key sensory and physical attributes and functional characteristics of affected foods to be maintained. Fat replacers are generally classified into three basic categories: fat-based, protein-based and carbohydrate-based. These categories and the most important examples within them are discussed below: • Fat-based substitutes. Sucrose fatty acid polyesters

(SPEs) are mixtures of compounds called esters made by combining sucrose esters and fatty acids, the most common example of which is olestra. Because of its large molecular size, olestra is not absorbed or metabolized by the body, thus it contributes no calories to the diet. Olestra is currently approved by FDA as a frying medium for savory snacks but has the potential to be included in frying oils and shortenings. Sucrose fatty acid esters (SFEs) are similar to SPEs however, their molecular size is smaller. As a result, they are partially or fully absorbed thus providing up to 9 calories per gram to the diet, the same as provided by conventional fats. SFEs are used as emulsifiers and stabilizers in a wide variety of foods and as components of coatings used to retard spoilage of fruits. Structured lipids are triglycerides which may be made from a variety of combinations of short, medium and long chain fatty acids. They are primarily used to reduce the amount of fat available for absorption, thereby reducing caloric value. Salatrim is an example of a structured lipid which is partially metabolized thus providing only about 5 calories per gram energy.

• Protein-based fat replacers. These materials are derived from a variety of protein sources including

eggs, milk, whey, soy and wheat gluten. Generally these proteins undergo a process called microparticulation in which they are sheared under heat into very small particles to impart similar mouthfeel and texture as conventional fats. They are used in frozen dairy desserts, cheese baked goods, sauces and salad dressings and may provide only 1-4 calories per gram depending on the water level incorporated into them.

• Carbohydrate-based fat replacers. A number of carbohydrates including gums, starches, pectins and cellulose have been used for many years as thickening agents to add bulk, moisture and textural stability to a wide variety of foods including puddings, sauces, soups, bakery goods, salad dressings and frozen desserts. Digestible carbohydrates such as modified starches and dextrins provide 4 calories per gram, while nondigestible complex carbohydrates provide virtually no calories.

In response to consumer demand of recent years, food manufacturers have developed a wide variety of reduced fat food products utilizing fat substitutes as a primary method of fat reduction. Since 1990 an average of over 1,000 new low fat foods have entered the marketplace annually bearing nutrient content claims of lowered fat (55). In 1996 the introduction of new low fat foods reached a peak at 2,076 products. Since 1996, however, introductions of new reduced or low fat products have declined to 1,405 products in 1997 and 1,180 in 1998. VI. FACTORS AFFECTING PHYSICAL

CHARACTERISTICS OF FATS AND OILS The physical characteristics of a fat or oil are dependent upon the degree of unsaturation, the length of the carbon chains, the isomeric forms of the fatty acids, molecular configuration, and the type and extent of processing. A. Degree of Unsaturation of Fatty Acids Food fats and oils are made up of triglyceride molecules which may contain both saturated and unsaturated fatty acids. Depending on the type of fatty acids combined in the molecule, triglycerides can be classified as mono-, di-, and triunsaturated as illustrated below.

C. Isomeric Forms of Fatty Acids Generally speaking, fats that are liquid at room

temperature tend to be more unsaturated than those that appear to be solid. It is not necessarily true, however, that all fats which are liquid at room temperature are high in unsaturated fatty acids. For example, coconut oil has a high level of saturates, but many are of low molecular weight, hence this oil melts at or near room temperature. Thus, the physical state of the fat does not necessarily indicate the amount of unsaturation.

For a given fatty acid chain length, saturated fatty acids will have higher melting points than those that are unsaturated The melting points of unsaturated fatty acids are profoundly affected by position and conformation of the double bonds. For example, the monounsaturated fatty acid oleic acid and its geometric isomer elaidic acid have different melting points. Oleic acid is liquid at temperatures considerably below room temperature, whereas elaidic acid is solid even at temperatures above room temperature. It is the presence of isomeric fatty acids in many vegetable shortenings and margarines that contributes substantially to the semi-solid form of these products. Thus, the presence of different geometric isomers of fatty acids influences the physical characteristics of the fat.

The degree of unsaturation of a fat, i.e., the number of double bonds present, normally is expressed in terms of the iodine value of the fat. Iodine value is the number of grams of iodine which will react with the double bonds in 100 grams of fat and may be calculated from the fatty acid composition obtained by gas chromatography. The average iodine value of unhydrogenated soybean oil is generally in the 125-140 range. A typical food service salad and cooking oil made from partially hydrogenated soybean oil may have an iodine value of about 105-120. A typical semi-solid household shortening made from partially hydrogenated soybean oil may have an iodine value of about 90-95. On the other hand, butterfat, which has a much lower level of unsaturated fatty acids than most shortenings made from partially hydrogenated soybean oil, typically has an iodine value of about 30.

D. Molecular Configuration of Triglycerides The molecular configuration of triglycerides can also affect the properties of a fat or oil. Melting points of fats will vary in their sharpness depending on the number of different chemical entities which are present. A simple triglyceride will have a sharp melting point. A mixture of triglycerides, as is typical of lard and most vegetable shortenings, will have a broad melting range. In the case of cocoa butter, the palmitic, stearic, and oleic acids are combined in two predominant triglyceride forms. The presence of these forms give cocoa butter its sharp melting point, just slightly below body temperature. The way cocoa butter melts is one of the reasons for the pleasant eating quality of chocolate.

B. Length of Carbon Chains in Fatty Acids As the chain length of the saturated fatty acid increases, the melting point also increases (Table I). Thus, a short chain saturated fatty acid such as butyric acid has a lower melting point than saturated fatty acids with longer chains. Some of the higher molecular weight unsaturated fatty acids, such as oleic acid also have relatively low melting points (Table II). The melting properties of triglycerides are related to those of their fatty acids. This explains why coconut oil, which contains almost 90% saturated fatty acids but with a high proportion of relatively short chain low melting fatty acids, is a clear liquid at 80°F in contrast to lard which contains only about 37% saturates, most with longer chains, is semi-solid at 80ºF.

A mixture of several triglycerides has a lower melting point than would be predicted for the mixture based on the melting points of the individual components. The mixture will also have a broader melting range than any of its components. Monoglycerides and diglycerides have higher melting points than triglycerides with a similar fatty acid composition.

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E. Polymorphism of Fats Solidified fats exhibit polymorphism, i.e., they can exist in several different crystalline forms, depending on the manner in which the molecules orient themselves in the solid state. The crystal forms of fats can transform from lower melting to successively higher melting modifications. The rate of transformation and the extent to which it proceeds are governed by the molecular composition and configuration of the fat, crystallization conditions, and the temperature and duration of storage. In general, fats containing diverse assortments of molecules (such as rearranged lard) tend to remain indefinitely in lower melting crystal forms, whereas fats containing a relatively limited assortment of molecules (such as soybean stearine) transform readily to higher melting crystal forms. Mechanical and thermal agitation during processing and storage at elevated temperatures tend to accelerate the rate of crystal transformation. The crystal form of the fat has a marked effect on the melting point and the performance of the fat in the various applications in which it is utilized. Food technologists apply controlled polymorphic crystal formation in the preparation of household shortenings and margarines. These products are predominantly partially hydrogenated soybean oil. In order to obtain desired product plasticity, functionality, and stability, the shortening or margarine must be in a crystalline form called “beta-prime” (a lower melting polymorph). Partially hydrogenated soybean oil tends to crystallize in the “beta” crystal form (a higher melting polymorph). Beta-prime crystal formation is promoted in a soybean oil product through inclusion of beta-prime promoting fats such as hydrogenated cottonseed or palm oils. Beta-prime is a smooth, small, fine crystal whereas beta is a large, coarse, grainy crystal. Shortenings and margarines are smooth and creamy because of the inclusion of beta-prime fats. VII. PROCESSING A. General Food fats and oils are derived from oilseed and animal sources. Animal fats are generally heat rendered from animal tissues to separate them from protein and other naturally occurring materials. Rendering may be either with dry heat or with steam. Rendering and processing of meat fats is conducted in USDA inspected plants. Vegetable fats are obtained by the extraction or the expression of the oil from the oilseed source.

Historically, cold or hot expression methods were used. These methods have been replaced with solvent extraction or pre-press/solvent extraction methods which give a better oil yield. In this process the oil is extracted from the oilseed by hexane (a light petroleum fraction) and the hexane is then separated from the oil, recovered, and reused. Because of its high volatility, no hexane residue remains in the finished oil after processing. The fats and oils obtained directly from rendering or from the extraction of the oilseeds are termed “crude” fats and oils. Crude fats and oils contain varying but relatively small amounts of naturally occurring non-glyceride materials that are removed through a series of processing steps. For example, crude soybean oil may contain small amounts of protein, free fatty acids, and phosphatides which must be removed through subsequent processing to produce the desired shortening and oil products. Similarly, meat fats may contain some free fatty acids, water, and protein which must be removed. It should be pointed out, however, that not all of the nonglyceride materials are undesirable elements. Tocopherols, for example, perform the important function of protecting the oils from oxidation and provide vitamin E. Processing is carried out in such a way as to control retention of these substances. Partial hydrogenation is employed frequently to improve the stability of fats and oils and to provide increased usefulness by imparting a semi-solid consistency to the fat for many food applications. It is agreed by most nutritionists and food technologists that the modern processing of edible fats and oils is the single factor most responsible for upgrading the quality of the fat consumed in the U.S. diet today. B. Degumming Crude oils having relatively high levels of phosphatides (e.g., soybean oil) may be degummed prior to refining to remove the majority of those phospholipid compounds. The process generally involves treating the crude oil with a limited amount of water to hydrate the phosphatides and make them separable by centrifugation. Soybean oil is the most common oil to be degummed; the phospholipids are often recovered and further processed to yield a variety of lecithin products. C. Refining The process of refining (sometimes referred to as “alkali refining”) generally is performed on vegetable oils to reduce the free fatty acid content and to remove

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F. Fractionation (Including Winterization) other gross impurities such as phosphatides, proteinaceous, and mucilaginous substances. By far the most important and widespread method of refining is the treatment of the fat or oil with an alkali solution. This results in a large reduction of free fatty acids through their conversion into water-soluble soaps. Most phosphatides and mucilaginous substances are soluble in the oil only in an anhydrous form and upon hydration with the caustic or other refining solution are readily separated. Oils low in phosphatide content (palm and coconut) may be physically refined (i.e., steam stripped) to remove free fatty acids. After alkali refining, the fat or oil is water-washed to remove residual soap.

Fractionation is the removal of solids by controlled crystallization and separation techniques involving the use of solvents or dry processing. Dry fractionation encompasses both winterization and pressing techniques and is the most widely practiced form of fractionation. It relies upon the differences in melting points and triglyceride solubility to separate the oil fractions. Winterization is a process whereby material is crystallized and removed from the oil by filtration to avoid clouding of the liquid fraction at cooler temperatures. The term winterization was originally applied decades ago when cottonseed oil was subjected to winter temperatures to accomplish this process. Winterization processes using temperature to control crystallization are continued today on several oils. A similar process called dewaxing is utilized to clarify oils containing trace amounts of clouding constituents.

D. Bleaching The term “bleaching” refers to the process for removing color producing substances and for further purifying the fat or oil. Normally, bleaching is accomplished after the oil has been refined.

Pressing is a fractionation process sometimes used to separate liquid oils from solid fat. This process presses the liquid oil from the solid fraction by hydraulic pressure or vacuum filtration. This process is used commercially to produce hard butters and specialty fats from oils such as palm and palm kernel.

The usual method of bleaching is by adsorption of the color producing substances on an adsorbent material. Acid-activated bleaching earth or clay, sometimes called bentonite, is the adsorbent material that has been used most extensively. This substance consists primarily of hydrated aluminum silicate. Anhydrous silica gel and activated carbon also are used as bleaching adsorbents to a limited extent.

Solvent fractionation is the term used to describe a process for the crystallization of a desired fraction from a mixture of triglycerides dissolved in a suitable solvent. Fractions may be selectively crystallized at different temperatures after which the fractions are separated and the solvent removed. Solvent fractionation is practiced commercially to produce hard butters, specialty oils, and some salad oils from a wide array of edible oils.

E. Deodorization Deodorization is a vacuum steam distillation process for the purpose of removing trace constituents that give rise to undesirable flavors, colors and odors in fats and oils. Normally this process is accomplished after refining and bleaching.

G. Hydrogenation The deodorization of fats and oils is simply a removal of the relatively volatile components from the fat or oil using steam. This is feasible because of the great differences in volatility between the substances that give flavors, colors and odors to fats and oils and the triglycerides. Deodorization is carried out under vacuum to facilitate the removal of the volatile substances, to avoid undue hydrolysis of the fat, and to make the most efficient use of the steam.

Hydrogenation is the process by which hydrogen is added directly to points of unsaturation in the fatty acids. Hydrogenation of fats has developed as a result of the need to (1) convert liquid oils to the semi-solid form for greater utility in certain food uses and (2) increase the oxidative and thermal stability of the fat or oil. Hydrogenation is an extremely important process as far as our food supply is concerned, because this processing imparts the desired stability and other properties to many edible oil products. The level of unsaturated fatty acids present in some oils such as soybean oil is reduced in order for the oils to have functional properties in many food applications. Hydrogenation is the only practical way to impart these properties.

Deodorization does not have any significant effect upon the fatty acid composition of most fats or oils. In the case of vegetable oils, sufficient tocopherols remain in the finished oils after deodorization to provide stability.

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H. Interesterification In the process of hydrogenation, hydrogen gas is reacted with oil at elevated temperature and pressure in the presence of a catalyst. The catalyst most widely used is nickel supported on an inert carrier which is removed from the fat after the hydrogenation processing is completed. Under these conditions, the gaseous hydrogen reacts with the double bonds of the unsaturated fatty acids as illustrated below:

Another process used by oil processors permits a rearrangement or a redistribution of the fatty acids on the glycerol fragment of the molecule. This process, referred to as interesterification, is accomplished by catalytic methods at relatively low temperature. Under some conditions the fatty acids are distributed in a more random manner than they were present originally. Other conditions permit the rearrangement process to direct the fatty acid distribution to an extent that allows further modification of shortening properties to be obtained. The rearrangement process does not change the degree of unsaturation or the isomeric state of the fatty acids as they transfer in their entirety from one position to another.

Lard in its natural state possesses a very narrow

temperature range over which it has good consistency for practical use in the kitchen. At slightly above normal room temperature, ordinary lard becomes somewhat softer than desirable, and at temperatures slightly lower, it becomes somewhat firmer than is desirable. Molecularly rearranged lard shortenings have a satisfactory consistency over a much wider temperature range.

The hydrogenation process is easily controlled and can be stopped at any desired point. As hydrogenation progresses, there is generally a gradual increase in the melting point of the fat or oil. If the hydrogenation of cottonseed or soybean oil, for example, is stopped after only a small amount of hydrogenation has taken place, the oils remain liquid. These partially hydrogenated oils are typically used to produce institutional cooking oils, liquid shortenings and liquid margarines. Further hydrogenation can produce soft but solid appearing fats which still contain appreciable amounts of unsaturated fatty acids and are used in solid shortenings and margarines. When oils are more fully hydrogenated, many of the carbon to carbon double bonds are converted to single bonds increasing the level of saturation. This conversion also affects trans fatty acids eliminating them from fully hydrogenated fats. If an oil is hydrogenated completely, the carbon to carbon double bonds are eliminated completely and the resulting product is a hard brittle solid at room temperature.

The predominant commercial application for interesterification in the US is the production of specialty fats for the confectionery and vegetable dairy industries. This process permits further tailoring of triglyceride properties to achieve the required steep melting curves. I. Esterification For the most part, fatty acids are present in nature in the form of esters and are consumed as such. Triglycerides, the predominant constituents of fats and oils, are examples of esters. When consumed and digested, fats are hydrolyzed initially to diglycerides and monoglycerides which are also esters. Carried to completion, these esters are hydrolyzed to glycerol and fatty acids. In the reverse process, esterification, an alcohol such as glycerol is reacted with an acid such as a fatty acid to form an ester such as mono-, di-, and triglycerides. In an alternative esterification process, called alcoholysis, an alcohol such as glycerol is reacted with fat or oil to produce esters such as mono- and diglycerides. Using the foregoing esterification processes, edible acids, fats, and oils can be reacted with edible alcohols to produce useful food ingredients that include many of the emulsifiers listed in the following section.

The hydrogenation conditions can be varied by the manufacturer to meet certain physical and chemical characteristics desired in the finished product. This is achieved through selection of the proper temperature, pressure, time, catalyst, and starting oils. Both positional and geometric (trans) isomers are formed to some extent during hydrogenation, the amounts depending on the conditions employed. Biological hydrogenation of polyunsaturated fatty acids occurs in some animal organisms, particularly in ruminants. This accounts for the presence of some trans isomers that occur in the tissues and milk of ruminants. 20

J. Emulsifiers Many foods are processed and/or consumed as emulsions, which are dispersions of immiscible liquids such as water and oil, e.g., milk, mayonnaise, ice cream, icings, and sausage. Emulsifiers, either present naturally in one or more of the ingredients or added separately, provide emulsion stability. Lack of stability results in separation of the oil and water phases. Some emulsifiers also provide valuable functional attributes in addition to

emulsification. These include aeration, starch and protein complexing, hydration, crystal modification, solubilization, and dispersion. Typical examples of emulsifiers and the characteristics they impart to food are listed in Table III. Emulsifiers must be sanctioned for use by the Food and Drug Administration (FDA). This agency provides guidelines for industry usage as GRAS (generally recognized as safe) or regulated food additives.

TABLE III EMULSIFIERS AND THEIR FUNCTIONAL CHARACTERISTICS

IN PROCESSED FOODS Emulsifier Characteristic Processed Food Mono-diglycerides Emulsification of water in oil

Anti-staling or softening Prevention of oil separation

Margarine Bread and rolls Peanut butter

Lecithin Viscosity control and wetting Anti-spattering and anti-sticking

Chocolate Margarine

Lactylated mono-diglycerides Aeration Gloss enhancement

Batters (cake) Confectionery coating

Polyglycerol esters Crystallization promoter Aeration Emulsification

Sugar syrup Icings and cake batters

Sucrose fatty acid esters Emulsification Bakery products

Sodium steroyl lactylate (SSL) Calcium steroyl lactylate (CSL)

Aeration, dough conditioner, stabilizer

Bread and rolls

K. Additives and Processing Aids Manufacturers may add low levels of approved food additives to fats and oils to protect their quality in processing, storage, handling, and shipping of finished products. This insures quality maintenance from time of

production to time of consumption. When addition provides a technical effect in the end-use product, the material added is considered a direct additive. Such usage must comply with FDA regulations governing levels, mode of addition, and product labeling. Typical examples of industry practice are listed in Table IV.

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Table IV SOME DIRECT FOOD ADDITIVES USED IN FATS AND OILS

Additive Effect Provided Tocopherols Butylated hydroxyanisole (BHA) Butylated hydroxytoluene (BHT) Tertiary butylhydroquinone (TBHQ)

Antioxidant, retards oxidative rancidity

Carotene (pro-vitamin A) Color additive, enhances color of finished foods

Methyl silicone (dimethylpolysiloxane) Inhibits oxidation tendency and foaming of fats and oils during frying

Diacetyl Provides buttery odor and flavor to fats and oils

Lecithin Water scavenger to prevent lipolytic rancidity

Citric acid Phosphoric acid

Metal chelating agents, inhibit metal-catalyzed oxidative breakdown

When addition is made to achieve a technical effect during processing, shipping, or storage and followed by removal or reduction to an insignificant level, the material added is considered to be a processing aid. Typical examples of processing aids and provided

effects are listed in Table V. Use of processing aids also must comply with federal regulations which specify good manufacturing practices and acceptable residual levels.

TABLE V

SOME PROCESSING AIDS USED IN MANUFACTURING EDIBLE FATS AND OILS Aid Effect Mode of Removal Sodium hydroxide Refining aid Acid neutralization

Carbon/clay (diatomaceous earth)

Bleaching aid Filtration

Nickel Hydrogenation catalyst Filtration

Sodium methoxide Rearrangement catalyst Water or acid neutralization, filtration, and deodorization

Phosphoric acid Citric acid

Refining acids, metal chelators Neutralization with base, filtration, or water washing

Acetone Hexane Isopropanol

Crystallization media for fractionation of fats and oils

Solvent stripping and deodorization

Nitrogen Oxygen replacement Diffusion

Polyglycerol esters Crystallization modification None

Silica hydrogel Adsorbent Filtration

Sodium lauryl sulfate Fractionation aid, wetting agent Washing and centrifugation

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VIII. REACTIONS OF FATS AND OILS A. Hydrolysis of Fats Like other esters, glycerides can be hydrolyzed readily. Partial hydrolysis of triglycerides will yield mono- and diglycerides and fatty acids. When the hydrolysis is carried to completion with water in the presence of an acid catalyst, the mono-, di-, and triglycerides will hydrolyze to yield glycerol and fatty acids. With aqueous sodium hydroxide, glycerol and the sodium salts of the component fatty acids (soaps) are obtained. In the digestive tracts of humans and animals and in bacteria, fats are hydrolyzed by enzymes (lipases). Lypolytic enzymes are present in some edible oil sources (i.e., palm fruit, coconut). Any residues of these lipolytic enzymes present in some crude fats and oils are deactivated by the temperatures used in oil processing, so enzymatic hydrolysis is unlikely in refined fats and oils. B. Oxidation of Fats 1. Autoxidation. Of particular interest in the food field is the process of oxidation induced by air at room temperature referred to as “autoxidation.” Ordinarily, this is a slow process which occurs only to a limited degree. In autoxidation, oxygen reacts with unsaturated fatty acids. Initially, peroxides are formed which in turn break down to hydrocarbons, ketones, aldehydes, and smaller amounts of epoxides and alcohols. Heavy metals present at low levels in fats and oils can promote autoxidation. Fats and oils often are treated with chelating agents such as citric acid (see Tables IV and V) to inactivate heavy metals.

The result of the autoxidation of fats and oils is the development of objectionable flavors and odors characteristic of the condition known as “oxidative rancidity.” Some fats resist this change to a remarkable extent while others are more susceptible depending on the degree of unsaturation, the presence of antioxidants, and other factors. The presence of light, for example, increases the rate of oxidation. It is a common practice in the industry to protect fats and oils from oxidation to preserve their acceptable flavor and shelf life. When rancidity has progressed significantly, it is apparent from the flavor and odor of the oil. Expert tasters are able to detect the development of rancidity in its early stages. The peroxide value determination, if used judiciously, may be helpful in measuring the degree of oxidative rancidity in the fat. It has been found that oxidatively abused fats can complicate nutritional and biochemical studies in

animals because they can affect food consumption under ad libitum feeding conditions and reduce the vitamin content of the food. If the diet has become unpalatable due to excessive oxidation of the fat component and is not accepted by the animal, a lack of growth by the animal could be due to its unwillingness to consume the diet. Thus, the experimental results might be attributed unwittingly to the type of fat or other nutrient being studied rather than to the condition of the ration. Knowing the oxidative condition of unsaturated fats is extremely important in biochemical and nutritional studies with animals. 2. Oxidation at Higher Temperatures. Although the rate of oxidation is greatly accelerated at higher temperatures, oxidative reactions which occur at higher temperatures may not follow precisely the same routes and mechanisms as the reactions at room temperatures. Thus, differences in the stability of fats and oils often become more apparent when the fats are used for frying or slow baking. The more unsaturated the fat or oil, the greater will be its susceptibility to oxidative rancidity. Predominantly unsaturated oils such as soybean, cottonseed, or corn oil are less stable than predominantly saturated oils such as coconut oil. Methylsilicone often is added to institutional frying fats and oils to reduce oxidation tendency and foaming at elevated temperatures. Frequently, partial hydrogenation is employed in the processing of liquid vegetable oil to increase the stability of the oil. Also oxidative stability has been increased in many of the oils developed through biotechnological engineering. The stability of a fat or oil may be predicted to some degree by the oxidative stability index (OSI). C. Polymerization of Fats All commonly used fats and particularly those high in polyunsaturated fatty acids tend to form some larger molecules known broadly as polymers when heated under extreme conditions of temperature and time. Under normal processing and cooking conditions polymers are formed in insignificant quantities. Although the polymerization process is not understood completely, it is believed that polymers in fats and oils arise by formation of either carbon to carbon bonds or oxygen bridges between molecules. When an appreciable amount of polymer is present, there is a marked increase in viscosity. Animal studies have shown that any polymers that may be present in a fat or oil are absorbed poorly from the intestinal tract and are excreted as such in the feces.

D. Reactions during Heating and Cooking Glycerides are subject to chemical reactions (oxidation, polymerization, hydrolysis) which can occur particularly during deep fat frying. The extent of these reactions, which may be reflected as a decrease in iodine value of the fat and an increase in free fatty acids, depends on the frying conditions, principally the temperature, aeration, and duration. The composition of a frying fat also may be affected by the kind of food being fried. For example, when frying high fat foods such as chicken, some fat from the food will be rendered and blend with the frying fat and some frying fat will be absorbed by the food. In this manner the fatty acid composition of the frying fat will change as frying progresses. Since absorption of fat by the fried food may be extensive, it is often necessary to replenish the fryer with fresh fat. This replacement with fresh fat tends to dilute overall compositional changes of the fat during prolonged frying. Frying conditions do not, however, saturate the unsaturated fatty acids, although the ratio of saturated to unsaturated fatty acids will change due to some polymerization of unsaturated fatty acids. It is the usual practice to discard frying fat when (1) prolonged frying causes excessive foaming of the hot fat, (2) the fat tends to smoke excessively, usually from prolonged frying with low fat turnover, or (3) an undesirable flavor or dark color develops. Any or all of these qualities associated with the fat can decrease the quality of the fried food. The “smoke,” “flash,” and “fire points” of a fatty material are standard measures of its thermal stability when heated in contact with air. The smoke point is the temperature at which smoke is first detected in a laboratory apparatus protected from drafts and provided with special illumination. The temperature at which the fat smokes freely is usually somewhat higher. The flash point is the temperature at which the volatile products are evolved at such a rate that they are capable of being ignited but not capable of supporting combustion. The fire point is the temperature at which the volatile products will support continued combustion. For typical fats with a free fatty acid content of about 0.05%, the smoke, flash, and fire points are around 420º, 620º, and 670º F, respectively. The degree of unsaturation of an oil has little, if any, effect on its smoke, flash, or fire points. Oils containing fatty acids of low molecular weight such as coconut oil, however, have lower smoke, flash, and fire points than other animal or vegetable fats of comparable free fatty acid content. Oils subjected to extended use will have

increased free fatty acid content resulting in a lowering of the smoke, flash and fire points. Accordingly used oil freshened with new oil will show an increased smoke, flash and free points. For additional details see Bailey’s Industrial Oil and Fat Products (56). It is important to note that all oils will burn if overheated. This is why most household fat and oil products for cooking carry a warning statement on their labels about potential fire hazards. Accordingly, careful attention must be given to all frying operations. When heating fat, do not leave the pan unattended. The continuous generation of smoke from a frying pan or deep fryer is a good indication that the fat is being overheated and could ignite if high heating continues. If smoke is observed during a frying operation, the heat should be reduced. If, however, the contents of the frying pan do ignite, extinguish the fire by covering the pan immediately with a lid or by spraying it only with an appropriate fire extinguisher. Do not attempt to remove a burning pan of oil from the stove. Allow the covered frying container to cool. Under no circumstances should burning fat be dumped into a kitchen sink or sprayed with water. Furthermore, if a consumer wishes to save the fat or oil after cooking, the hot fat or oil should never be poured back into its original container. Most containers for cooking oils are not designed to withstand the high temperatures reached by the oil during cooking. Pouring hot oil into such containers could result in breakage or melting of the container and possible burns to the user. Considerable work has been done studying the effects of elevated temperatures on the composition and biological qualities of edible fats and oils. Much of this work has been done with temperatures and other conditions which simulated those experienced in commercial deep frying operations, such as in restaurants or food processing establishments. Other studies, however, have exposed the foods to exaggerated conditions that are unrealistic and not indicative of actual use conditions. Under these unrealistic conditions, some substances are formed in small amounts that when isolated and fed at concentrated levels can be shown to be toxic to laboratory animals. The practical significance of these observations was defined more clearly in a two-year animal feeding study by Nolen et al (57). This work showed that animals consuming used typical frying fats as the sole source of fat in the diet throughout their life span thrived equally as well as control animals consuming the same fat that had not been subjected to frying conditions. Clark, et al. also have reviewed the nutritional aspects of heated fats (58).

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IX. PRODUCTS PREPARED FROM FATS AND OILS

A. General A wide variety of products based on edible fats and oils is available to the consuming public. Shortenings, margarines, spreads, butter, salad and cooking oils, mayonnaise, salad dressing, French, Italian, and other specialty salad dressings, and confectioners’ coatings are some of the widely available products that are based entirely on fats and oils or contain fat or oil as a principal ingredient. Many of these products also are sold in commercial quantities to food processors, snack food manufacturers, bakeries, restaurants, and institutions. Dietary fats have been categorized as “visible” and “invisible” sources of fat. Visible fats are defined for statistical reporting purposes as those that have been isolated from animal tissues, oilseeds, or vegetable sources, and are used in such products as shortening, margarine, and salad oil. These fats and oils comprise about 43% of the total fat available for consumption in the U.S. diet. Invisible fats are those that have not been isolated from the animal tissues, oilseeds, or vegetable sources, and are consumed as part of the animal tissues or the vegetables in the diet. These comprise the remaining 57% of the fat available for consumption in the U.S. diet. The contribution of the major sources of visible fat or oil consumed in this country and the amount of each available for consumption in various food products are provided in Table VI. The data given in Table VI

include both retail and commercial availability of each fat or oil. It also should be recognized that the table does not include invisible fats, i.e., those consumed as part of meat, fish, poultry, eggs, dairy products, and other foods (see Table X). Several vegetable oils of lesser importance in the U.S. but available in some products include rice bran, shea nut, illipe, sal, almond, and avocado. The typical fatty acid composition of the principal vegetable oils and animal fats used for food purposes in the U.S. is given in Table VII. The typical fatty acid composition of oils derived from biotechnological means generally tend to be higher in monounsaturates (e.g., oleic acid) to reduce the need for hydrogenation as a stabilizing process. Other genetically modified oils have less saturates (e.g., palmitic) or less polyunsaturates (e.g., linolenic) depending on the end use of the oil. Genetically modified oils of the future will likely have customized fatty acid composition to meet specific applications. The ingredient statement of a packaged food product lists the source oils (along with all other ingredients) which are or may be present in the product. All ingredients are listed in descending order of predominance. Current FDA labeling regulations state that if a fat or oil is the predominant ingredient of a food product (e.g., salad and cooking oil, shortening, or margarine), the actual source oil used must be shown on the product label. However, for foods in which a fat or oil is not the predominant ingredient (e.g., baked products or snack foods) and for which a manufacturer may wish to substitute one oil for another depending on commodity prices and availability, the manufacturer is permitted to list the alternative oils that may be present.

25

26

TABLE VI FATS AND OILS USED IN FOOD

(million pounds)

Shortening Source Oils: (Baking and Frying Fats) Margarine Salad and Cooking Oil Totals1 Fiscal Year 70/71 80/81 90/91 95/96 70/71 80/81 90/91 95/96 70/71 80/81 90/91 95/96 70/71 80/81 90/91 95/96Vegetable Oils Soybean 2,077 2,675 4,090 4,702 1,381 1,666 1,811 1,699 2,288 4,226 4,693 5,317 5,780 8,610 10,722 11,877Canola -- -- -- -- -- -- -- -- -- -- -- 211 -- -- -- 319Corn D2 D 304 82 188 217 195 79 202 383 589 434 403 624 1,143 595Cottonseed 194 132 272 218 64 27 D D 479 382 438 235 805 555 777 497Palm 143 215 D D -- -- -- -- -- -- -- -- 160 291 98 DCoconut3 -- -- -- -- -- -- -- -- -- -- -- -- 220 338 169 221Peanut -- -- -- -- -- -- -- -- 156 105 129 D 181 119 129 129Sunflower3 -- -- -- -- -- -- -- -- -- -- -- -- -- 79 166 90 Meat Fats Edible Tallow 496 730 498 335 -- -- -- -- -- -- -- -- 508 740 501 341Lard 509 328 277 266 1544 954 394 334 -- -- -- -- 1,612 415 314 297

Total Vegetable and Meat Fats5 3,599 4,224 5,793 5,603 1,792 2,022 2,168 1,811 3,402 5,280 6,222 6,197 9,669 11,908 14,491 14,366 1 May include other edible uses besides shortening, margarine, and salad and cooking oil

2 D - Withheld to avoid disclosing figures for individual companies.3 Data on usage in specific product categories unavailable 4 Includes lard and edible tallow.5 Components do not add to totals due to rounding, avoiding disclosures , and not including minor oils (e.g., safflower) in product categories

Source: Economic Research Service of the U.S. Department of Agriculture

27

Table VII TYPICAL FATTY ACID COMPOSITION OF THE PRINCIPAL VEGETABLE

AND ANIMAL FATS AND OILS IN THE U.S.1

(% of total fatty acids)

BU

TYR

IC

CA

PRO

IC

CA

PRY

LIC

CA

PRIC

LAU

RIC

MY

RIS

TIC

PALM

ITIC

STEA

RIC

AR

AC

HID

IC

PALM

ITO

LEIC

OLE

IC

GA

DO

LEIC

LIN

OLE

IC

LIN

OLE

NIC

SATURATED

| MONO- | | UNSATURATED |

POLYUN-SATURATED

Oil or Fat 4:0 6:0 8:0 10:0 12:0 14:0 16:0 18:0 20:0 16:1 18:1 20:1 18:2 18:3 Soybean oil 11 4 24 54 7

Corn oil 11 2 28 58 1

Cottonseed oil 1 22 3 1 19 54 1

Palm oil 1 45 4 40 10

Peanut oil2 11 2 1 48 2 32

Olive oil 13 3 1 1 71 10 1

Canola oil 4 2 62 22 10

Safflower oil 7 2 13 78

Sunflower oil 7 5 19 68 1

Mid oleic sunflower oil 4 5 65 26

Coconut oil 1 8 6 47 18 9 3 6 2

Palm kernel oil 3 4 48 16 8 3 15 2

Cocoa butter 26 34 1 34 3

Butterfat3 4 2 1 3 3 11 27 12 2 29 2 1

Lard 2 26 14 3 44 1 10

Beef tallow4 3 24 19 4 43 3 1

1Fatty acid composition data determined by gas-liquid chromatography and provided by member companies of the Institute of Shortening and Edible Oils, Inc. Fatty acids (designated as number of carbon atoms: number of double bonds) occurring in trace amounts are excluded. Component fatty acids may not add to 100% due to rounding. 2Peanut oil typically contains C22:0 plus C24:0 at 4-5% of total fatty acids. 3Butterfat typically contains C15:0 plus C17:0 at about 3% of total fatty acids. 4Beef tallow typically contains C15:0 plus C17:0 at about 2% and C14:1 plus C17:1 at about 2% of total fatty acids. B. Salad and Cooking Oils Salad and cooking oils are prepared from vegetable oils that are refined, bleached, deodorized, and sometimes dewaxed or lightly hydrogenated and winterized. Soybean and corn oil are the principal oils sold in this form, although cottonseed, peanut, safflower, sunflower, canola and olive oil also are used. Advanced plant breeding technology, much of which includes

biotechnology applications, has resulted in a wide variety of new oils that may be used as salad and cooking oils. These newer oils include high oleic canola, safflower, soybean and sunflower oils, low linolenic canola and soybean oils, mid oleic sunflower oil, and linola oil. When soybean oil is processed into salad and cooking oil intended for household use, a refined, bleached, and deodorized oil often is suitable. This is because under the usual conditions of handling (e.g., the

28

oil is not reused for cooking) and storage, the linolenic acid naturally present in the oil is not highly susceptible to oxidation which might produce undesirable odors and flavors in the oil. On the other hand, if the oil is intended for use as a cooking oil for applications involving prolonged and repeated heating (e.g., in restaurants), hydrogenation or blending with other oils usually is desirable to improve stability. C. Shortenings (Baking and Frying Fats) Shortenings are fats used in the preparation of many foods. Because they impart a “short” or tender quality to baked goods, they are called shortenings. For many years, lard and other animal fats were the principal edible fats used in shortenings in this country, but during the last third of the nineteenth century they were replaced by cottonseed oil, a by-product of the cotton industry. Many types of vegetable oils including soybean, cottonseed, corn, sunflower, and palm can be used in shortening products. (See Table VI.) Hydrogenated shortenings may be made from a single hydrogenated fat, but are usually made from a blend of two or more hydrogenated fats. For example, partially hydrogenated cottonseed or palm oil may be blended with partially hydrogenated soybean oil for improved performance properties, such as creamy consistency and good storage stability. The conditions and extent of hydrogenation may be varied for each source oil to achieve the characteristics desired. Thus, in

the manufacture of hydrogenated shortenings, considerable flexibility is possible providing a wide choice of finished product characteristics. Research findings of the past 30 years have suggested the advisability of increasing the level of polyunsaturated fatty acids in the diet. As a result the manufacturers of household vegetable shortenings have provided such products containing a polyunsaturated fatty acid range of 3-15%. Lard and other animal fats and mixtures of animal and vegetable fats also are used in shortening. Mixtures of animal and vegetable fats frequently are hydrogenated to some extent to obtain the physical characteristics desired. Lard is sometimes used in commercial applications such as in the baking of pastry and bread. Liquid shortenings have become increasingly popular among food service facilities over the past two decades due to their desired pourability in replenishing deep fat fryers. These lightly hydrogenated shortenings usually have polyunsaturated fatty acid contents ranging from 25-50%. These products also have been used in some commercial baking and frying applications. Table VIII gives the ranges in fatty acid composition for typical household and food service shortening products made from all vegetable fat or from animal/vegetable fat blends. The composition ranges given for both types of shortening are based on information available for products in broad distribution in the U.S.

Table VIII

FATTY ACID COMPOSITION OF TYPICAL HOUSEHOLD AND FOOD SERVICE SHORTENINGS

Type of Shortening

Monounsaturated

% of Total Fatty Acids Polyunsaturated

Saturated

All vegetable fat 45-65 3-15 22-30 Animal/vegetable fat blend 45-51 3-10 30-50

D. Hard Butters The term hard butter describes a collection of specialty fats that are designed to either replace or extend cocoa butter (cocoa butter alternatives) and/or butterfat. They are used primarily in confectionery and vegetable dairy applications and are generally characterized by a steep melting profile. Cocoa butter alternative fats are often placed into one of three categories:

1. Cocoa Butter Equivalents have physicochemical

characteristics similar to cocoa butter. They are derived from fats like illipe or kokum and fractions of shea, palm, or sal. They are highly compatible with cocoa butter.

2. Cocoa Butter Substitutes are predominantly lauric based and may involve processing techniques like hydrogenation, interesterification and fractionation. They exhibit an extremely limited compatibility with cocoa butter.

3. Cocoa Butter Replacers are formulated from non-lauric fats (palm, soybean, cottonseed, etc.) that have been subjected to partial hydrogenation or a combination of the former and fractionation. They can tolerate as much as 25% cocoa butter, depending upon the product.

E. Margarine and Spreads Margarine and spreads are prepared by blending fats and/or oils with other ingredients such as water and/or milk products, suitable edible proteins, salt, flavoring and coloring materials and Vitamins A and D. Margarine must contain at least 80% fat by federal regulation, however, “diet” margarines and spreads may contain 0-80% fat.

Margarine and spreads are available in stick, tub, liquid and spray forms. They may be formulated from vegetable oils and/or animal fats, however, the vast preponderance of such products are made from vegetable oils. The fat in margarine and spreads may be prepared from a wide variety of fat combinations and may be the result of several processes. The more common preparations used include blends of hydrogenated fat(s) and unhydrogenated oils(s), blends of two or more hydrogenated fats, a single hydrogenated fat or a blend of liquid unhydrogenated oil interesterified with a fully saturated fat. Table IX provides the range in fatty acid composition for various types of margarine and spread products currently available in the retail market.

TABLE IX FATTY ACID COMPOSITION OF FATS AND OILS

IN TYPICAL MARGARINES, SPREADS AND BUTTER FAT Product

Monounsaturated

% of Total Fatty Acids Polyunsaturated

Saturated

Stick margarine - all vegetable 30-55 12-35 15-21 - animal & vegetable 46-52 9-19 29-40 Tub Type spreads1 - all vegetable 30-50 25-45 10-19 Butterfat2 25-33 1-4 63-70

1Spreads are margarine-like products containing less than 80% fat. (Currently the average fat content is 54%.) 2Butterfat contains about 0.2-0.4% arachidonic acid. The data for saturated fatty acids include the contributions of C4, C6, C8, and C10 saturated fatty acids, which represent about 10% of total fatty acids.

F. Butter Butter must contain not less than 80% by weight of butterfat. The butterfat in the product serves as a plastic matrix enclosing an aqueous phase consisting of water, casein, minerals, and other soluble milk solids. These solids usually constitute about 1% of the weight of the butter. Frequently, salt is added at levels from 1.5-3.0% of the weight of the product. Butter is an important source of vitamin A, and to a lesser extent, of vitamin D. Butterfat, like other fats and oils, is comprised of triglycerides, but is characterized by the fact that a substantial portion of the fatty acids are relatively short chain saturated acids. The fatty acid composition for typical butterfat is given in Tables VII and IX. G. Dressings for Food

1. Mayonnaise and Salad Dressing. Mayonnaise and salad dressing are emulsified, semi-

solid fatty foods that by federal regulation must contain not less than 65% and 30% vegetable oil, respectively, and dried whole eggs or egg yolks. Salt, sugar, spices, seasoning, vinegar, lemon juice, and other ingredients complete these products.

2. Pourable-Type Dressings. The pourable dressings may be two phase (e.g., vinegar and oil) or the emulsified viscous type (e.g., French). There is a great variety of products available of varying compositions with a wide range in their oil content. Italian, French and Roquefort types are representative of this class. A federal standard for French dressing requires a vegetable oil content of not less than 35%. Some other ingredients that may be used in the preparation of the pourable dressings are salt, sugar, emulsifiers, spices, seasonings, and acidifying agents, such as vinegar, citric acid, lemon or lime juice.

3. Reduced Calorie Dressings. The current interest to reduce caloric intake as a means of weight control has resulted in the introduction of a wide variety

29

of products containing fewer or no calories. “Reduced” calorie products contain at least 25% fewer calories than the conventional products and are achieved primarily by substituting carbohydrates and water for fat.

4. Reduced Fat, Low Fat, and Fat Free Dressings. In order to satisfy consumer demand for reduced fat foods, the food industry has developed a wide array of dressings, which have been reduced in fat content. In accordance with regulatory standards, dressings containing 3 grams or less fat per serving may be described as “low fat”, whereas a dressing containing 25% less fat than the conventional dressing may be declared as “reduced fat.” Other dressings containing less than 0.5 gram fat per serving may be described as “fat free” or “containing no fat.” H. Toppings, Coffee Whiteners, Confectioners Coatings, and Other Formulated Foods Vegetable fats are used in a variety of convenience foods such as nondairy toppings, coffee whiteners, and party dips, as well as confectioners’ coatings for soft cakes and candy. Cocoa butter, palm kernel oil, and hydrogenated coconut oil are used extensively because of their physical characteristics. I. Lipids for Special Nutritional Applications In recent years special lipids referred to as “medium chain triglycerides” (MCT) containing C6 to C10 saturated fatty acids have been used in particular clinical applications. Certain modifications of MCTs are soluble in both oil and water systems and are metabolized more rapidly than conventional fats and oils. Whereas conventional fats and oils are absorbed slowly and transported via the lymphatic system, MCTs are absorbed relatively quickly and transported via the portal system. Because of their unique ability to pass through the intestinal epithelium directly into the portal system, MCTs have become the standard lipid used in the treatment of various fat malabsorption syndromes. Other MCT applications include their use as rapidly available energy sources for patients with intestinal resection or short bowel syndrome and for premature infants. In certain liquid formula diets and intravenous fluids, MCTs may be combined in varying proportions with corn oil, soybean oil, or safflower oil. X. TRENDS IN FAT CONSUMPTION The trends of food fat consumption (availability) in the U.S. since 1970 are summarized in Table X. Total

per capita fat consumption increased 5.2 pounds over the period 1970 to 1994. During this same time period the per capita consumption of visible fats (i.e., contained in foods added to the diet) has increased by 16.0 pounds while that of invisible fats (i.e., naturally occurring in foods) decreased by 9.8 pounds. Most of the decline in invisible fats consumption has been attributable to a decrease in fat consumed in meat, poultry and fish from 42.8 to 31.3 pounds during the same time period. This is thought to be the result of consumers reducing red meat intake, selecting leaner red meat cuts, and consuming more fish and poultry which contain relatively lower amounts of fat. The per capita increase in visible fat consumption has been largely the result of increased salad and cooking oil consumption. This increase is probably the result of greater consumption of fried foods in food service establishments and increased use of salad oils on salads consumed both away from and at home. The increasing consumption of foods away from the home is significantly affecting the intake of certain nutrients, particularly fat. Lin et al (59), found that in 1977-78 fat from both home and away-from-home foods provided 41% of calories consumed. By 1995 foods eaten at home contributed only 31.5% of calories from fat whereas foods eaten away-from-home contributed 37.6% of calories from fat. While this trend clearly shows a significant reduction in overall dietary fat, it indicates away-from-home foods have shown smaller reductions in fat compared to at-home meals. Among visible fats in the diet, vegetable fats experienced a 44% increase in per capita consumption from 1970 (38.5 pounds) to 1997 (55.4 pounds) compared to a 27% decrease in animal fats consumption (14.1 pounds in 1970 vs. 10.3 pounds in 1997) (Table X). This dietary trend reflects the substitution of vegetable fats for animal fats over the past three decades. These changes are also reflected in the levels of specific fatty acids in the diet. Polyunsaturated fatty acid intake per capita increased 15% from 1970 to 1994 (27 g/person/day vs. 31 g/person/day), monounsaturated fatty acid intake experienced little change, and saturated fatty acid intake decreased by about 15% (61 g/person/day in 1970 vs. 52 g/person/day in 1994) (ERS, USDA, 1998). Baking and frying fats (shortening) experienced a modest increase in per capita consumption of almost 21% between 1970 and 1997. Fats from margarines and spreads, butter, and “other” foods such as coffee whiteners, confections and non-dairy toppings have all experienced respective reductions in per capita consumption of 21%, 23% and 52% during the same time period.

30

31

TABLE X

CONSUMPTION (AVAILABILITY) OF VISIBLE AND INVISIBLE FATS (1970-1997)1

(pounds per person)

Sources by Food Group 1970 1975 1980 1985 1990 1991 1992 1993 1994 1995 1996 1997

Visible Fats (added fats) Butter2 4.3

ntent

3.8 3.6 3.9 3.8 3.5 3.8 3.7 3.9 3.6 3.5 3.3 Margarine and Spreads2,3 8.7 8.8 9.0 8.6 8.7 8.5 8.8 8.9 7.9 7.4 7.3 6.9 Lard4 4.6 3.2 2.6 1.8 1.9 1.7 1.7 1.7 2.3 2.2 2.3 2.3 Edible Tallow4,5 -- -- 1.1 1.9 0.5 1.4 2.4 2.2 2.4 2.7 3.0 3.4 Baking and Frying Fats (shortening)

17.3 17.0 18.2 22.9 22.2 22.4 22.4 25.1 24.1 22.5 22.3 20.9

Salad and Cooking Oils

15.4 17.9 21.2 23.6 24.8 26.7 27.2 26.8 26.3 26.9 26.1 28.3 Other6 2.3

) 2.0 1.5 1.6 1.2 1.3 1.4 1.7 1.6 1.6 1.4 1.1

(Total Fat Co Animal Source

14.1 10.8 12.3 13.3 9.7 9.7 10.6 10.5 11.4 11.3 11.1 10.3 Vegetable Source 38.5 41.9 44.8 50.9 53.1 55.7 56.8 59.7 57.2 55.5 54.7 55.4 Total Visible Fats 52.6 52.6 57.2 64.3 62.8 65.4 67.4 70.2 68.6 66.9 65.8 65.6

Invisible Fats (naturally occuring)7

tent)

Dairy Products (excluding butter)

15.6 14.9 14.9 15.7 15.4 15.5 15.6 15.7 15.7 -- -- -- Eggs 3.5 3.2 3.1 2.9 2.6 2.6 2.7 2.7 2.7 -- -- -- Meat, Poultry, Fish 42.8 37.3 39.0 37.2 33.5 30.5 31.1 30.8 31.3 -- -- -- Fruits and Vegerables

1.1 1.1 1.1 1.2 1.3 1.2 1.3 1.3 1.3 -- -- --

Legumes, Nuts, Soy

4.2 4.6 3.8 5.0 4.9 4.9 4.8 4.8 4.6 -- -- -- Grains 1.9 1.8 1.8 2.0 2.6 2.6 2.7 2.7 2.8 -- -- -- Miscellaneous8 2.1 1.9 2.0 2.6 3.0 3.1 3.2 3.0 2.9 --

--

--

(Total Fat Con Animal Source

61.9 55.4 57.0 55.8 51.5 48.6 49.4 49.2 49.7 -- -- -- Vegetable Source 9.3 9.4 8.7 10.8 11.8 11.8 12.0 11.8 11.6 -- -- -- Total Invisible Fats

71.2 64.7 65.7 66.6 63.3 60.4 61.4 61.0 61.4 --

--

--

Total Visible and Invisible Fats and Oils9

123.8 117.3 122.9 130.9 126.2 125.8 128.7 131.1 129.0 --

--

--

1 Components may not add to totals due to rounding.

2 Fat Content. 3 Includes indirect use of edible tallow and lard (I.e., animal/vegetable blends).

4 Direct use. 5 Data for direct use of edible tallow not available prior to 1979. 6 Includes confections, coffee whiteners, and non-dairy toppings. 7 Data for invisible fat not available after 1994. 8 Includes chocolate, cocoa, coffee, tea and spices. Source: Economic Research Service

9 Fats deliberately discarded not accounted for in these data U.S. Department of Agriculture

Data presented in Agricultural Economic Report No. 138, “Food Consumption, Prices, Expenditures,” July 1968, showed that on a per capita basis about two-thirds of the visible fat available in 1940 was from animal origin and about one-third from vegetable origin. In contrast to this, the report shows that in 1966 only one-third of the visible fat available was from animal origin while two-thirds was from vegetable origin. In 1997 this trend continued further and vegetable oils now contribute about 95% of the visible fat available for consumption (see Table X). Since around 1940 animal

fats have gone from a very predominant to a very subordinate position as far as their contribution to the visible fat portion of the diet is concerned. Concurrently, vegetable oils have advanced from a very subordinate to a very dominant position. Here again, the data are based upon the quantity of fats and oils available for consumption by the civilian population. The amount of fat actually consumed currently is about 33% of total calories (see Table XI).

TABLE XI NUTRIENT INTAKES: MEAN PERCENTAGES OF CALORIES FROM PROTEIN, FAT,

AND CARBOHYDRATE, BY SEX AND AGE, 1 DAY, 19961 Sex and age (years)

Percentage of

population

Protein

Total

fat

Saturated fatty acids

Monounsaturated

fatty acids

Polyunsaturated

fatty acids

Carbohydrate Percent --------------------------------------- Percent of calories ------------------------------------ Males: 20 and over

33.9

15.8

33.2

11.1

12.8

6.6

49.6

Females: 20 and over

36.8

15.4

32.2

10.6

12.2

6.9

52.7

All Individuals

100.00

15.1

32.7

11.2

12.5

6.5

52.1

1Total population surveyed = 5,188 individuals. Source: reference (1) XI. CONCLUSION This booklet has reviewed a broad scope of topics including the importance of dietary fat as an essential nutrient and the usage of fats and oils in a variety of food products. Much research continues on the

role of dietary fat in relation to health. As a service to the professional communities, the Institute of Shortening and Edible Oils, Inc., intends to revise this publication as needed to keep the information as current and useful as possible.

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References: Food Fats and Oils - 1999 1. Agricultural Research Service, U.S. Department of Agriculture, Data Tables: Results from USDA’s 1994-96 Continuing Survey of Food Intakes by Individuals and 1994-96 Diet and Health Knowledge Survey, Riverdale, MD, p. 12, 1997. 2. Subcommittee on the Tenth Edition of the RDAs, Food and Nutrition Board, Commission on Life Sciences, National Research Council, Recommended Dietary Allowances, 10th ed. Washington, D.C., National Academy Press, pp.46-49, 1989. 3. Committee on Diet and Health, Food and Nutrition Board, Commission on Life Sciences, National Research Council, Diet and Health, Implications for Reducing Chronic Disease Risk, Washington, D.C., National Academy Press, 1989. 4. Center for Nutrition Policy and Promotion, U.S. Department of Agriculture, Is total fat consumption really decreasing? Nutrition Insights, No. 5, 2 pp., 1998. 5. Hunter, J. E. and Applewhite, T. H., Correction of Dietary Fat Availability Estimates for Wastage of Food Service Deep-Frying Fats. J. Am. Oil Chem. Soc., 70: 613-617, 1993. 6. U.S. Department of Agriculture and U.S. Department of Health and Human Services, Nutrition and Your Health: Dietary Guidelines for Americans, 4th ed., Home and Garden Bulletin #232, Washington, D.C., 1995. 7. American Heart Association, 1998 Heart and Stroke Statistical Update, Dallas, TX, American Heart Association, 1997. 8. National Cholesterol Education Program, Report of the Expert Panel on Population Strategies for Blood Cholesterol Reduction. Executive Summary, Washington, D.C., U.S. Department of Health and Human Services, NIH Publication 90-3047, 1990. 9. National Cholesterol Education Program, Second report of the expert panel on detection, evaluation, and treatment of high blood cholesterol in adults (Adult Treatment Panel II), Circulation, 89: 1333-1445, 1994. 10. Committee on Nutrition, American Academy of Pediatrics, Statement on Cholesterol. Pediatrics, 90: 469-473, 1992.

11. Mattson, F. H. and Grundy, S. M., Comparison of effects of dietary saturated, monounsaturated, and polyunsaturated fatty acids on plasma lipids and lipoproteins in man. J. Lipid Res., 26: 194-202, 1985. 12. Mata, P., Garrido, J. A., Ordovas, J. M., Blazquez, E., Alvarez-Sala, L. A., Rubio, M. J., Alfonso, R., and de Oya, M., Effect of dietary monounsaturated fatty acids on plasma lipoproteins and apolipoproteins in women. Am. J. Clin. Nutr., 56: 77-83, 1992. 13. Gardner, C. D. and Kraemer, H. C., Monounsaturated versus polyunsaturated dietary fat and serum lipids. A meta-analysis. Arterioscler. Thromb. Vasc. Biol., 15: 1917-1927, 1995. 14. Aro, A., Jauhiainen, M., Partanen, R., Salminen, I., and Mutanen, M., Stearic acid, trans fatty acids, and dairy fat: effects on serum and lipoprotein lipids, apolipoproteins, lipoprotein(a), and lipid transfer proteins in healthy subjects. Am. J. Clin. Nutr., 65: 1419-1426, 1997. 15. Almendingen, K., Jordal, O., Kierulf, P., Sanstad, B., and Pedersen, J. I., Effects of partially hydrogenated fish oil, partially hydrogenated soybean oil, and butter on serum lipoproteins and Lp[a] in men. J. Lipid Res., 36: 1370-1384, 1995. 16. Gardner, C. D., Fortmann, S. P., and Krauss, R. M., Association of small low-density lipoprotein particles with the incidence of coronary artery disease in men and women. J. Am. Med. Assn., 276: 875-881, 1996. 17. Fiber, lipids, and coronary heart disease. A statement for healthcare professionals from the Nutrition Committee, American Heart Association. Circulation, 95: 2701-2704, 1997. 18. American Cancer Society, Cancer Facts and Figures - 1998, Atlanta, GA, American Cancer Society, Inc., 1998. 19. Hunter, D. J., Spiegelman, D., Adami, H.-O., et al, Cohort studies of fat intake and the risk of breast cancer--a pooled analysis. N. Engl. J. Med., 334: 356-361, 1996. 20. ILSI North America, Workshop on Individual Fatty Acids and Cancer, Am J. Clin Nutr., 66: 1505S-1586S, 1997.

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21. Zock, P. L. and Katan, M. B., Linoleic acid intake and cancer risk: a review and meta-analysis. Am. J. Clin. Nutr., 68: 142-153, 1998. 22. Hunter, J. E., and Applewhite, T. H., Reassessment of trans fatty acid availability in the U.S. diet. Am J. Clin. Nutr., 54: 363-369, 1991. 23. Allison, D. B., Egan, K., Barraj, L. M., Caughman, C., Infante, M., and Heimbach, J. T., Estimated intakes of trans fatty and other fatty acids in the U.S. population. J. Am. Diet. Assoc., 99: 166-174, 1999. 24. Kris-Etherton, P. M. and Nicolosi, R. J., Trans Fatty Acids and Coronary Heart Disease Risk, Washington D.C., International Life Sciences Institute, 1995. 25. ASCN/AIN Task Force on Trans Fatty Acids, Position paper on trans fatty acids. Am. J. Clin. Nutr., 63: 663-670, 1996. 26. Van Poppel, G., on behalf of the TRANSFAIR Study Group, Intake of trans fatty acids in Western Europe: the TRANSFAIR Study. The Lancet, 351: 1099, 1998. 27. Mensink R. P. and Katan, M. B., Effects of dietary trans fatty acids on high-density and low-density lipoprotein cholesterol levels in healthy subjects. N. Engl. J. Med., 323: 439-445, 1990. 28. Judd, J. T., Clevidence, B. A., Muesing, R. A., Wittes, J., Sunkin, M. E., and Podczasy, J. J., Dietary trans fatty acids: effects on plasma lipids and lipoproteins of healthy men and women. Am. J. Clin. Nutr., 59: 861-868, 1994. 29. Clevidence, B. A., Judd, J. T., Schaefer, E. J., Jenner, J. L., Lichtenstein, A. H., Muesing, R. A., Wittes, J., and Sunkin, M. E., Plasma lipoprotein(a) levels in men and women consuming diets enriched in saturated, cis, or trans monounsaturated fatty acids. Arterio. Thromb. Vasc. Biol., 17: 1657-1661, 1997. 30. Judd, J., Baer, D., Clevidence, B., Kris-Etherton, P., Muesing, R., Iwane, M., and Lichtenstein, A., Blood lipid and lipoprotein modifying effects of trans monounsaturated fatty acids compared to carbohydrate, oleic acid, stearic acid, and C12:0-16:0 saturated fatty acids in men fed controlled diets. FASEB J., 12: A229, 1998.

31. Willett, W. C., Stampfer, M. J., Manson, J. E., Colditz, G. A., Speizer, F. E., Rosner, B. A., Sampson, L. A., and Hennekens, C. H., Intakes of trans fatty acids and risk of coronary heart disease among women. Lancet 341: 581-585, 1993. 32. National Center for Health Statistics, Health United States 1996-97 and Injury Chartbook, DHHS Publication No. (PHS) 97-1232, Department of Health & Human Services, Hyattsville, MD, p. 130, 1997. 33. British Nutrition Foundation, Report of the British Nutrition Foundation Task Force. Trans Fatty Acids, London, The British Nutrition Foundation, 1995. 34. Emken, E. A., ed., Trans fatty acids: infant and fetal development. Report of an Expert Panel on Trans Fatty acids and Early Development, Am. J. Clin .Nutr., 66: 715S-736S, 1997. 35. Ip, C. and Marshall, J. R., Trans fatty acids and cancer. Nutr. Revs., 54: 138-145, 1996. 36. Decker, E. A., The role of phenolics, conjugated linoleic acid, carnosine, and pyrroloquinoline quinone as nonessential dietary antioxidants. Nutr. Revs., 53: 49-58, 1995. 37. Chin, S. F., Liu, W., Storkson, J. M., Ha, Y. L., and Pariza, M. W., Dietary sources of conjugated dienoic isomers of linoleic acid, a newly recognized class of anticarcinogens. J. Food Comp. Anal., 5: 185-197, 1992. 38. Ha, Y. L., Grimm, N. K., and Pariza, M. W., Anticarcinogens from fried ground beef: heat-altered derivatives of linoleic acid. Carcinogenesis, 8: 1881-1887, 1987. 39. Pariza, M. W. and Hargraves, W. A., A beef-derived mutagenesis modulator inhibits initiation of mouse epidermal tumors by 7,12-dimethylbenz[a]anthracene. Carcinogenesis 6: 591-593, 1985. 40. Ha, Y. L., Storkson, J., and Pariza, M. W., Inhibition of benzo[a]pyrene-induced mouse forestomach neoplasia by conjugated dienoic derivatives of linoleic acid. Cancer Res., 50: 1097-1101, 1990. 41. Ip, C., Scimeca, J. A., and Thompson, H. J., Conjugated linoleic acid. A powerful anticarcinogen from animal fat sources. Cancer, 74: 1050-1054, 1994.

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42. Ip, C., Scimeca, J. A., and Thompson, H. J., Effect of timing and duration of dietary conjugated linoleic acid on mammary cancer prevention. Nutr. Cancer, 24: 241-247, 1995. 43. Ip, C., Briggs, S. P., Haegele, A. D., Thompson, H. J., Storkson, J., and Scimeca, J. A., The efficacy of conjugated linoleic acid in mammary cancer prevention is independent of the level or type of fat in the diet. Carcinogenesis, 17: 1045-1050, 1996. 44. Ip, C., Jiang, C., Thompson, H. J., and Scimeca, J. A., Retention of conjugated linoleic acid in the mammary gland is associated with tumor inhibition during the post-initiation phase of carcinogenesis. Carcinogenesis, 18: 755-759, 1997. 45. Thompson, H., Zhu, Z., Banni, S., Darcy, K., Loftus, T., and Ip, C., Morphological and biochemical status of the mammary gland is influenced by conjugated linoleic acid: implication for a reduction in mammary cancer risk. Cancer Res., 57: 5067-5072, 1997. 46. Lee, K. N., Kritchevsky, D., and Pariza, M. W., Conjugated linoleic acid and atherosclerosis in rabbits. Atherosclerosis, 108: 19-25, 1994. 47. Nicolosi, R. J., Rogers, E. J., Kritchevsky, D., Scimeca, J. A., and Huth, P. J., Dietary conjugated linoleic acid reduces plasma lipoproteins and early atherosclerosis in hypercholesterolemic hamsters. Artery, 22: 266-277, 1997. 48. Park, Y., Albright, K. J., Liu, W., Storkson, J. M., Cook, M. E., and Pariza, M. W., Effect of conjugated linoleic acid on body composition in mice. Lipids, 32: 853-858, 1997. 49. Pariza, M. W., Conjugated linoleic acid, a newly recognized nutrient. Chemistry & Industry, pp. 464-466, 1997. 50. Lees, A. M., Mok, H. Y. I., Lees, R. S., McCluskey, M. A., and Grundy, S. M., Plant sterols as cholesterol

lowering agents – clinical trials in patients with hypercholesterolemia and studies of sterol balance. Atherosclerosis, 28: 325-338, 1977. 51. Miettinen, T. A., Puska, P., Gylling, H., Vanhanen, H., and Vartiainen, E., Reduction of serum-cholesterol with sitosterol-ester margarine in a mildly hypercholesterolemic population. N. Engl. J. Med., 333: 1308-1312, 1995. 52. Weststrate, J. A. and Meijer, G. W., Plant sterol-enriched margarines and reduction of plasma total- and LDL-cholesterol concentrations in normocholesterolaemic and mildly hypercholesterolaemic subjects. Eur. J. Clin. Nutr., 52: 334-343, 1998. 53. Hefle, S. L. and Taylor, S. L., Allergenicity of edible oils. Food Technol., 53: 62-70, 1999. 54. James, C., Global status of transgenic crops in 1997. ISAAA Briefs, No. 5, Ithaca, NY, ISAAA, p. v, 1997. 55. Dornblaser, L., Traditional nutritionals continue to fade. New Product News, p. 11, March 1999. 56. Hui, Y. H., ed., Bailey’s Industrial Oil and Fat Products, vol. 2, Edible Oil and Fat Products: Oils and Oilseeds, 5th ed., New York, John Wiley & Sons, Inc., p. 214, 1996. 57. Nolen, G. A., Alexander, J. C., and Artman, N. R., Long term rat feeding study with used frying oils. J. Nutr., 93: 337-347, 1967. 58. Clark, W. L., Nagle, N. E., Elder, B. D., and Weiss, T. J., Nutritional aspects of frying fats-- an overview. J. Am. Oil Chem. Soc., Abstract #91, 55: 244A, 1978. 59. Lin, B.-H., Guthrie, J., and Frazao, E., Away-From-Home Food Increasingly Important to Quality of American Diet. Agriculture Information Bulletin No. 749, Economic Research Service, U. S. Department of Agriculture, 12 pp., 1999.

Glossary

Antioxidant A substance that slows or interferes with the reaction of a fat or oil with

oxygen. The addition of antioxidants to fats or foods containing them retards rancidity and increases stability and shelf life.

Bleaching The purification process to remove color bodies and residual impurities from refining, generally through the use of an adsorbent clay material.

Biotechnology The use of living organisms or other biological systems to develop food, drugs and other products.

Catalyst A material which accelerates a chemical reaction without becoming part of the reaction products.

Cholesterol A fat-soluble sterol found primarily in animal cells important in physiological processes.

Chlorophyll A natural, green coloring agent vital to a plant’s photosynthesis process which is removed from vegetable oils through bleaching and refining processes.

Cis The term applied to a geometric isomer of an unsaturated fatty acid where the hydrogen atoms attached to the carbon atoms comprising the double bond are on the same side of the carbon chain.

Complex triglyceride A triglyceride where one or two fatty acid structures differ from the third fatty acid.

Confectionery fat A broad range of fats used in the formulation of sweet goods such as candy bars, bakery product coatings, cream centers, and granola bars.

Conjugated fatty acids

Polyunsaturated fatty acids exhibiting pairs of unsaturated carbons not separated by at least one saturated carbon.

Crude oil The oil product obtained from the initial extraction, crushing or expelling of an animal or vegetable source.

Degumming The process that removes phosphatide compounds from crude oils prior to refining.

Deodorization The process of subjecting oil to high temperatures in the presence of a vacuum to remove trace volatile components that may affect flavor, odor and color. It is generally the last step in the refining process.

Diglyceride The ester resulting from the chemical combination of glycerol and two fatty acids.

Double bond The configuration of two adjacent carbon atoms with dual linkage between the carbons.

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Emulsifier Compounds having the ability to alter the surface properties of the

materials they contact. Emulsifiers are often used to disperse immiscible liquids such as water and oil or fats in products such as mayonnaise, ice cream and salad dressings.

Ester The chemical reaction product of an alcohol and an acid.

Esterification The process of chemically combining an alcohol and an acid resulting in the formation of an ester.

Fat Esters of fatty acids and glycerol which are normally solid at room temperature.

Fatty Acid A chemical unit composed of a chain of carbon and hydrogen atoms ending with a reactive group consisting of carbon, hydrogen and oxygen which is the fundamental unit within a triglyceride fat molecule.

Fully refined oil The term used to describe an oil which has been subjected to extensive processing methods to remove: (1) free fatty acids and other gross impurities (refine), (2) naturally occurring color bodies such as chlorophyll (bleach), and (3) volatile trace components which may affect color, flavor and odor (deodorize).

Fire point The temperature at which an oil sample, when heated under prescribed conditions, will ignite for a period of at least five seconds.

Flash point The temperature at which an oil sample, when heated under prescribed conditions, will flash when a flame is passed over the surface of the oil.

Fractionation The process of separating fats and oils by differences in melt points or volatility.

Free fatty acids The fatty acids in a fat which are not chemically bound to glycerol molecules.

Fully hydrogenated The term describing a fat or oil which has been hydrogenated to the extent that the resultant product is solid at room temperature. Products containing hydrogenated fats include “heavy duty” frying fats for restaurant use, solid shortenings and solid margarines.

Geometric isomer An isomer differing because of the structural location of certain elements.

Hard butter A generic term used primarily in the confectionery industry to describe a class of fats with physical characteristics similar to those of cocoa butter or dairy butter.

Hydrogenation The process of adding hydrogen atoms to the carbon-to-carbon double bonds in unsaturated fatty acids. This process results in higher melt points, higher solid fat content and longer shelf life without rancidity in fat-containing products.

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Hydrolysis The chemical reaction of fat with water to form glycerol and free fatty

acids.

Interesterification The process of rearranging the fatty acids in triglyceride molecules. It is used principally in confectionery fats and spreads to maintain solid fat content at ambient temperatures while lowering the melting point.

Iodine value An expression of the degree of unsaturation of a fat. It is determined by measuring the amount of iodine which reacts with a natural or processed fat under prescribed conditions.

Isomer Compounds containing the same elements in the same proportions which can exist in more than one structural form; e.g. geometric, positional or cyclic.

Lauric oils Oils containing 40-50% lauric acids (C-12) in combination with other relatively low molecular weight fatty acids. Coconut and palm kernel oils are principal examples.

Lecithin A mixture of naturally occurring phosphatides which has emulsifying, wetting and antioxidant properties, a principal source of which is crude soybean oil.

Lipid A broad spectrum of fat and fat-like compounds including mono-, di- and triglycerides, sterols, phosphatides and fatty acids.

Lipoprotein Any of the class of proteins that contain a lipid combined with a simple protein.

Medium chain triglyceride (MCT)

Triglycerides containing fatty acid chains of 6-10 carbon atoms which are readily absorbed by the body.

Monoglyceride The ester resulting from the combination of glycerol and one fatty acid.

Monounsaturated A fatty acid containing only one pair of carbon – carbon double bonds.

Non-conjugated fatty acids

Polyunsaturated fatty acids exhibiting pairs of carbons separated by at least one saturated carbon atom.

Oil Esters of fatty acids and glycerol which normally are liquid at room temperature.

Oleate An ester or salt of oleic acid. Commonly referenced as a preparation containing oleic acid as the principal ingredient.

Olein The liquid fraction of oil remaining when an oil is cooled.

Olean (olestra) A sucrose fatty acid polyester used as a substitute for dietary fat which is not digested or absorbed by the body.

Oxidation The reaction of oxygen with a fat or oil resulting in the development of rancidity.

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Partially hydrogenated

The term used to describe an oil which has been lightly to moderately hydrogenated to shift the melting point to a higher temperature range and increase the stability of the oil. Partially hydrogenated oils remain liquid and are used in a wide variety of food applications.

Peroxides The intermediate compounds formed during the oxidation of lipids which may react further to form the compounds that can cause rancidity.

Phosphatide The chemical combination of an alcohol (typically glycerol) with phosphoric acid and a nitrogen compound; synonymous with phospholipid.

Plasticize The process of creating a solid crystal structure in a fat or oil product resulting in a smooth appearance and firm consistency.

Polymerize The bonding of similar molecules into long chains or branched structures.

Polymorphism The property of a fat molecules to exist in multiple crystalline structures; identified as alpha, beta and beta prime.

Polyunsaturated A fatty acid containing more than one pair of carbon-carbon double bonds.

Positional isomer An isomer differing in the location of a double bond.

Refine The process of removing impurities from crude oil by way of treatment with alkali solution (chemical) or steam stripping (physical).

Saponification The chemical reaction between a fat or oil and an alkaline compound creating glycerol and soap.

Saturated A fatty acid containing no carbon-carbon double bonds.

Shortening A fat product that incorporates tenderness in the food (e.g., bakery products)in which it is used. It may carry other additives such as flavorings, colors, emulsifiers and preservatives.

Simple triglyceride A triglyceride comprised of three identical fatty acids.

Soap The product resulting from the treatment of fat with an alkali.

Soap stock The aqueous byproduct from the chemical refining operation that is comprised of soap, hydrated gums, water, oil and other impurities.

Stearine The solid fat product created by fractionation.

Stearic acid A saturated 18-carbon free fatty acid.

Sterol A compound made up of the sterol nucleus, an 8-10-carbon side chain and an alcohol group.

Tocopherol A naturally occurring antioxidant found in many vegetable oils.

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Trans A geometric isomer of an unsaturated fatty acid where hydrogens attached

to the carbons comprising the double bond are on opposite sides of the carbon chain.

Triglyceride The chemical combination product of glycerol and three fatty acids.

Unsaturated The carbon-hydrogen make-up of a fatty acid describing a shortage of hydrogen atoms in the molecule.

Wax The chemical combination of a long chain alcohol and fatty acids.

Winterize The process of separating the solid fraction (stearine) from the liquid fraction (olein) of an oil by cooling and filtering.

COMMON TEST METHODS AND RELATED TERMS Cold test The determination in time that an oil remains free of visible solids when immersed in a

32ºF ice-water bath.

Color, Lovibond An analytical method used to quantify the visual color of an oil in units of red and yellow.

Dropping point The temperature at which a solid fat softens to the point where it will flow and drop out of a specially designed container. The dropping point is an indication of the chemical and crystalline nature of the solid fat.

Flavor A sensory description experienced in taste testing of a fat or oil. A bland or neutral flavor is generally desirable.

Free fatty acid (FFA) The amount of free fatty acids present in an oil as determined by simple titration.

Melting point (MP) The temperature at which a fat changes from solid to liquid within the specific parameters of the test.

Oil stability index (OSI)

An accelerated rancidity test that measures the rate of oxidation of a fat or oil and is expressed as an index number. The higher the index number, at a given temperature, the more stable the product is to oxidation. This method replaces the Active Oxygen Method (AOM).

Peroxide value (PV) The determination of the extent of fat or oil oxidation by measuring the amount of peroxides present.

Solid fat index (SFI) Provides an index or indication of the proportions of crystallized and molten fat at a given series of temperature checkpoints. Determined by measuring the change in volume that occurs when a solid fat partially melts to liquid at the temperature of interest.

Solid fat content (SFC) A measure of the crystallized fat content measured by magnetic resonance (NMR) at a series of temperature checkpoints.

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