1 food preservation 1121 steven c seideman extension food processing specialist cooperative...

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FOOD PRESERVATION1121

Steven C SeidemanSteven C Seideman

Extension Food Processing SpecialistExtension Food Processing Specialist

Cooperative Extension ServiceCooperative Extension Service

University of ArkansasUniversity of Arkansas

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INTRODUCTION

Americans tend to take our food supply for Americans tend to take our food supply for granted. Compared to most of the world, we granted. Compared to most of the world, we have excellent soil and natural resources have excellent soil and natural resources that are second to none. Our growth and that are second to none. Our growth and harvesting of livestock and crops is cutting harvesting of livestock and crops is cutting edge and our food processing technology is edge and our food processing technology is state-of-the-art. In addition, our distribution state-of-the-art. In addition, our distribution and sales market are tops.and sales market are tops.

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INTRODUCTION

Our food would not be readily available to Our food would not be readily available to consumers if foods were not processed in consumers if foods were not processed in such a manner that they prevent or delay the such a manner that they prevent or delay the natural process of decay. natural process of decay.

The science behind food preservation can The science behind food preservation can be seen everyday in a supermarket although be seen everyday in a supermarket although the preservation method may not be readily the preservation method may not be readily known.known.

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HISTORY OF FOOD PRESERVATION

The caveman’s discovery of fire was probably the The caveman’s discovery of fire was probably the start of food preservation. By cooking meat on a start of food preservation. By cooking meat on a fire,the meat became pasteurized and the shelf-life fire,the meat became pasteurized and the shelf-life (time the food product is considered edible) was (time the food product is considered edible) was increased by several days. Then came the advent increased by several days. Then came the advent of drying meat which increased the shelf-life even of drying meat which increased the shelf-life even longer. longer.

Europeans later discovered that cheese and Europeans later discovered that cheese and sausages could be preserved by the use of low pH, sausages could be preserved by the use of low pH, low moisture content and high salt content. low moisture content and high salt content.

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Nicholas Appert under Napoleon invented the art Nicholas Appert under Napoleon invented the art of canning. He didn’t know how it worked but he of canning. He didn’t know how it worked but he found that food placed in cans or glass jars and found that food placed in cans or glass jars and heated would keep for a much longer period of heated would keep for a much longer period of time. time.

During the Revolutionary War, patriots often During the Revolutionary War, patriots often received barrels of salt pork from Uncle Sam’s received barrels of salt pork from Uncle Sam’s Provision Co, hence the expression “Uncle Sam” Provision Co, hence the expression “Uncle Sam” referring to the U.S. Federal government was referring to the U.S. Federal government was derived.derived.

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Starting in the early 1900s, the science of Starting in the early 1900s, the science of microorganisms along with the science of food microorganisms along with the science of food gathered momentum and lead to such inventions as gathered momentum and lead to such inventions as refrigeration, freezing, use of chemicals in foods such refrigeration, freezing, use of chemicals in foods such as sodium lactate and parabens, freeze drying and as sodium lactate and parabens, freeze drying and packaging.packaging.

Along with the above came improvements in cooking Along with the above came improvements in cooking procedures, blast freezing and other technological procedures, blast freezing and other technological advances to existing methods.advances to existing methods.

Now we are on the doorsteps of food irradiation, radio Now we are on the doorsteps of food irradiation, radio frequency cooking and other technologies.frequency cooking and other technologies.

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Food Preservation

This module is about methods used to This module is about methods used to preserve food and how they work.preserve food and how they work.

Other educational courses in this series also Other educational courses in this series also cover some of the same material but from cover some of the same material but from the standpoint of bacterial spoilage or the standpoint of bacterial spoilage or pathogens.pathogens.

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The Fundamental Concepts of Food Preservation

Basically, all food preservation methods do one or Basically, all food preservation methods do one or more of the following to prevent the natural more of the following to prevent the natural biodegradation of food. biodegradation of food.

*Prevent the proliferation of spoilage bacteria.*Prevent the proliferation of spoilage bacteria. *Prevent the proliferation of pathogenic bacteria.*Prevent the proliferation of pathogenic bacteria. *Prevent the rancidity of fat*Prevent the rancidity of fat *Prevent to work of endogenous autolytic enzymes.*Prevent to work of endogenous autolytic enzymes. *Prevent the reintroduction of dirt, dust etc after *Prevent the reintroduction of dirt, dust etc after

processing (e.g. packaging).processing (e.g. packaging).

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Preventing Proliferation of Spoilage and Pathogenic Bacteria Bacteria reduce the edibility of food and is, Bacteria reduce the edibility of food and is,

by far, the leading source of degradation of by far, the leading source of degradation of foods.foods.

Whether the bacteria be of the spoilage or Whether the bacteria be of the spoilage or pathogenic types, they are bacteria and can pathogenic types, they are bacteria and can be controlled by controlling the following 6 be controlled by controlling the following 6 conditions in food.conditions in food.

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CONDITIONS AFFECTING BACTERIAL GROWTH

There are 6 conditions affecting bacterial growth There are 6 conditions affecting bacterial growth and can be remembered by the anagram FAT and can be remembered by the anagram FAT TOM.TOM.

* Food* Food * Acidity* Acidity * Time* Time *Temperature*Temperature *Oxygen*Oxygen *Moisture*Moisture

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Conditions Affecting Bacterial Growth FOODFOOD Bacteria need food to reproduce.Bacteria need food to reproduce. High protein foods and moist starchy foods High protein foods and moist starchy foods

promote bacterial growth but any food can promote bacterial growth but any food can be potentially risky is not handled properly.be potentially risky is not handled properly.

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Conditions Affecting Bacterial Growth

ACIDITYACIDITY pH-measure of acidity or alkalinity. (pH =7 is pH-measure of acidity or alkalinity. (pH =7 is

neutral; 1=acid; 14=basic).neutral; 1=acid; 14=basic). Most bacteria prefer a pH of 5.5-7.5.Most bacteria prefer a pH of 5.5-7.5. Most pathogenic bacteria will not grow at a pH of Most pathogenic bacteria will not grow at a pH of

4.6 or less (acid). This is why fermented foods 4.6 or less (acid). This is why fermented foods such as sauerkraut (fermented cabbage) and such as sauerkraut (fermented cabbage) and fermented sausages were historically used in fermented sausages were historically used in Europe.Europe.

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pH VALUES OF BACTERIA

BacteriaBacteria

MoldsMolds

YeastsYeasts

SalmonellaSalmonella

Clostridium BotuliumClostridium Botulium

Clostridium perfringensClostridium perfringens

Listeria monocytogenesListeria monocytogenes

CampylobacterCampylobacter

pH RangepH Range

0.5-110.5-11

1.5-8.51.5-8.5

4.5-9.54.5-9.5

4.8-8.34.8-8.3

5.0-8.55.0-8.5

4.6-9.64.6-9.6

5.0-9.05.0-9.0

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pH VALUES FOR FOODS

FoodFood MeatMeat ChickenChicken FishFish FruitFruit ApplesApples GrapesGrapes VegetablesVegetables CarrotCarrot CornCorn DairyDairy MilkMilk CheeseCheese

pH RangepH Range5.1-6.25.1-6.26.2-6.46.2-6.46.6-6.86.6-6.82.9-4.72.9-4.7 2.9-3.32.9-3.3 3.4-4.53.4-4.54.8-6.04.8-6.0 4.9-5.24.9-5.2 7.37.3

6.6-6.56.6-6.5 4.9-5.94.9-5.9

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Conditions Affecting Bacterial Growth TIMETIME Under optimal conditions, some bacteria can Under optimal conditions, some bacteria can

double every 20 minutes and increase double every 20 minutes and increase logarithmically.logarithmically.

The colder the storage temperature, the longer the The colder the storage temperature, the longer the potential shelflife.potential shelflife.

Potentially hazardous foods should not remain in Potentially hazardous foods should not remain in the danger zone (40-140F) for more than 4 hours the danger zone (40-140F) for more than 4 hours during the entire food handling process.during the entire food handling process.

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Conditions Affecting Bacterial Growth

TEMPERATURETEMPERATURE*Bacterial proliferation can be controlled by *Bacterial proliferation can be controlled by

both heat and cold.both heat and cold. Bacteria generally do not grow at freezer Bacteria generally do not grow at freezer

temperatures but they can survive.temperatures but they can survive. Use of refrigeration temperatures (30-50F) Use of refrigeration temperatures (30-50F)

slows down the rate of bacterial slows down the rate of bacterial proliferation. The colder the better.proliferation. The colder the better.

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Degrees FDegrees F 250250 212212 160160 148148 137137 140-40140-40 9090 7070 6060 4040 3232 2828 14 14

Bacterial ActionBacterial ActionResistant spores killedResistant spores killedBoiling point of waterBoiling point of waterResistant Salmonella killResistant Salmonella killVegetative cells killedVegetative cells killedTrichina killedTrichina killedDANGER ZONEDANGER ZONEBacteria double-20 minBacteria double-20 minBacteria double-1 hourBacteria double-1 hourBacteria double-2 hoursBacteria double-2 hoursBacteria double –6 hoursBacteria double –6 hoursBacteria double-20 hoursBacteria double-20 hoursBacteria double –60 hoursBacteria double –60 hoursLower limit for bacteriaLower limit for bacteria

BACTERIAL THERMOMETER

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The Use of Heat

There are two important words to define;There are two important words to define; **PasteurizationPasteurization refers to the cooking of food refers to the cooking of food

where only a certain number of bacteria are where only a certain number of bacteria are killed. Pasteurization does not render the killed. Pasteurization does not render the product sterile.product sterile.

**SterilizationSterilization refers to the total destruction refers to the total destruction of all living organisms and is only found in of all living organisms and is only found in canned shelf- stable items.canned shelf- stable items.

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The Use of Heat

Clostridium botulinum is a bacteria that can form Clostridium botulinum is a bacteria that can form spores that are very resistant to heat. It produces a spores that are very resistant to heat. It produces a toxin that causes paralysis and is often fatal. It toxin that causes paralysis and is often fatal. It grows well in an anaerobic (no oxygen), warm grows well in an anaerobic (no oxygen), warm (60-115F) environment.(60-115F) environment.

Unless a food goes through the canning procedure Unless a food goes through the canning procedure (cook in a retort or pressure device of 212F for (cook in a retort or pressure device of 212F for several hours) it is assumed to have Clostridium several hours) it is assumed to have Clostridium spores present. spores present.

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Photo courtesy of USDA

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The Use of Heat

Remember that Clostridium grow best at Remember that Clostridium grow best at 60-115F so you must cool all foods fast 60-115F so you must cool all foods fast after heating.after heating.

Remember to assume that all foods except Remember to assume that all foods except shelf-stable canned foods and high acid shelf-stable canned foods and high acid foods contain Clostridium spores and treat foods contain Clostridium spores and treat them with the proper precautions.them with the proper precautions.

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Conditions Affecting Bacterial GrowthOXYGENOXYGEN

Some bacteria require oxygen to grow Some bacteria require oxygen to grow (aerobic).(aerobic).

Some bacteria will only grow if no oxygen Some bacteria will only grow if no oxygen is present (anaerobic).is present (anaerobic).

Some bacteria can go with or without Some bacteria can go with or without oxygen ( facultative).oxygen ( facultative).

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Conditions Effecting Bacterial Growth

MOISTUREMOISTURE The amount of water available in food for chemical The amount of water available in food for chemical

reactions and microbial growth is called water reactions and microbial growth is called water activity (Aw).activity (Aw).

Water activity is measured from 0 (totally dry) to Water activity is measured from 0 (totally dry) to 1.0 (pure water).1.0 (pure water).

Most spoilage and pathogenic bacteria can only Most spoilage and pathogenic bacteria can only grow in foods that have a water activity higher than grow in foods that have a water activity higher than 0.85.0.85.

The water activity available in foods can be reduced The water activity available in foods can be reduced by freezing, dehydration or adding salt or sugar.by freezing, dehydration or adding salt or sugar.(e.g. honey does not foster bacterial growth).(e.g. honey does not foster bacterial growth).

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WATER ACTIVITY Aw/ MicroorganismAw/ Microorganism1.0-0.95 Bacteria1.0-0.95 Bacteria

0.95-0.91 Bacteria0.95-0.91 Bacteria

0.91-0.87 Yeasts0.91-0.87 Yeasts

0.87-0.80 Molds0.87-0.80 Molds

0.30-0.20 No microorganism 0.30-0.20 No microorganism proliferationproliferation

FoodsFoodsMeat, fish, sausage, milkMeat, fish, sausage, milk

Cheese, cured meat (ham), fruit juice Cheese, cured meat (ham), fruit juice concconc

Fermented sausages (salami), dry Fermented sausages (salami), dry cheeses, margarinecheeses, margarine

Juice conc, syrups, flour, fruit cakes, Juice conc, syrups, flour, fruit cakes, honey, jellies, preserveshoney, jellies, preserves

Cookies, crackers, bread crustsCookies, crackers, bread crusts

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Preventing the Rancidity of Fat

Fats tend to go rancid over time. Fats tend to go rancid over time. Almost all foods have some level of fat.Almost all foods have some level of fat. Oxidative rancidity is the term used to explain the Oxidative rancidity is the term used to explain the

generation of a free radical and results in a rapid generation of a free radical and results in a rapid progression of fat rancidity.progression of fat rancidity.

The next slide will show some things that promote The next slide will show some things that promote rancidity (pro-oxidants) and some things that rancidity (pro-oxidants) and some things that retard its development (antioxidants).retard its development (antioxidants).

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Affectors of Fat Rancidity

Pro-oxidantsPro-oxidants

*Salt*Salt

*Time*Time

*Heat*Heat

*Oxygen*Oxygen

*Irradiation*Irradiation

AntioxidantsAntioxidants

*Vitamin C and E*Vitamin C and E

*Sodium nitrite (cured *Sodium nitrite (cured

meats)meats)

*Erythorbate/ *Erythorbate/

AscorbateAscorbate

*Smoke components*Smoke components

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Fat Rancidity

The eating of rancid fat has been shown to The eating of rancid fat has been shown to cause cancer.cause cancer.

In the same light, diets rich in antioxidants In the same light, diets rich in antioxidants have been shown to prevent cancer.have been shown to prevent cancer.

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Prevent the Work of Endogenous, Autolytic Enzymes Most raw food materials have endogenous, Most raw food materials have endogenous,

autolytic enzymes that decompose foods.autolytic enzymes that decompose foods. The best example is that of vegetables that The best example is that of vegetables that

require a heat treatment called “blanching” require a heat treatment called “blanching” that denatures the enzymes. If they are not that denatures the enzymes. If they are not blanched, these vegetables would turn blanched, these vegetables would turn mushy.mushy.

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Prevent the Reintroduction of Dirt, Dust etc

After food in treated or processed, it needs After food in treated or processed, it needs to be kept clean. This area is known as to be kept clean. This area is known as “packaging”.“packaging”.

Packaging can range from a simply plastic Packaging can range from a simply plastic film ( dust cover) all the way to flexible, film ( dust cover) all the way to flexible, oxygen impermeable films and even cans oxygen impermeable films and even cans and glass/ plastic jars. and glass/ plastic jars.

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Methods of Food Preservation

We have just discussed the fundamental We have just discussed the fundamental causes of food spoilage.causes of food spoilage.

We can now discuss the basic methods used We can now discuss the basic methods used to control food spoilage.to control food spoilage.

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Methods of Food Preservation

1)Control of temperature1)Control of temperature

Use of heatUse of heat

Use of refrigeration/ FreezingUse of refrigeration/ Freezing

2)Use of Food Ingredients2)Use of Food Ingredients

3)Control of Water Activity3)Control of Water Activity

4)Control of pH4)Control of pH

5)Packaging5)Packaging

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Control of Temperature

USE OF HEATUSE OF HEAT The use of heat can range from a mild cook in the The use of heat can range from a mild cook in the

kitchen for pasteurization to total sterilization kitchen for pasteurization to total sterilization Pasteurization refers to the application of heat to Pasteurization refers to the application of heat to

get a significant reduction in bacteria.get a significant reduction in bacteria. Sterilization refers to the application of a lot of Sterilization refers to the application of a lot of

heat and time to render the a food product totally heat and time to render the a food product totally bacteria-free.bacteria-free.

Pasteurization is mainly important in the reduction Pasteurization is mainly important in the reduction of pathogenic bacteria in milk-legally required.of pathogenic bacteria in milk-legally required.

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Control of Temperature

Heating of food also denatures endogenous Heating of food also denatures endogenous enzymes (blanching of vegetables).enzymes (blanching of vegetables).

The science of canning is aimed at the total The science of canning is aimed at the total destruction of all bacteria. The hardest bacteria to destruction of all bacteria. The hardest bacteria to kill is the spore-former, Clostridium botulinum kill is the spore-former, Clostridium botulinum which can be lethal.which can be lethal.

Cooking can be done in a variety of methods from Cooking can be done in a variety of methods from dry heat methods to deep-fat frying. dry heat methods to deep-fat frying.

All methods are aimed at the destruction, to some All methods are aimed at the destruction, to some degree of bacteria and inactivation of enzymes..degree of bacteria and inactivation of enzymes..

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BACTERIAL THERMOMETER Degrees FDegrees F 250250 212212 160160 148148 137137 140-40140-40 9090 7070 6060 4040 3232 2828 14 14

Bacterial ActionBacterial ActionResistant spores killedResistant spores killedBoiling point of waterBoiling point of waterResistant Salmonella killResistant Salmonella killVegetative cells killedVegetative cells killedTrichina killedTrichina killedDANGER ZONEDANGER ZONEBacteria double-20 minBacteria double-20 minBacteria double-1 hourBacteria double-1 hourBacteria double-2 hoursBacteria double-2 hoursBacteria double –6 hoursBacteria double –6 hoursBacteria double-20 hoursBacteria double-20 hoursBacteria double –60 hoursBacteria double –60 hoursLower limit for bacteriaLower limit for bacteria

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Photo courtesy of USDA

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Control of Temperature THE USE OF THE USE OF REFRIGERATION/FREEZING.REFRIGERATION/FREEZING. Refrigeration (at or above 32F) slows down bacteria Refrigeration (at or above 32F) slows down bacteria

proliferation and enzymatic activity.proliferation and enzymatic activity. Freezing (below 32F) dramatically slows down fat Freezing (below 32F) dramatically slows down fat

rancidity and enzymatic activity but they still rancidity and enzymatic activity but they still happen.Less than 1 year frozen shelf-life.happen.Less than 1 year frozen shelf-life.

Freezing does not kill bacteria to any great extent. They Freezing does not kill bacteria to any great extent. They just become dormant.just become dormant.

Fast freezing results in smaller ice crystals being formed Fast freezing results in smaller ice crystals being formed that do not damage the food structure upon thawing.that do not damage the food structure upon thawing.

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SHELFLIFE OF SELECTED FOODS

FoodFood Chicken (fresh)Chicken (fresh) Chicken (fried)Chicken (fried) BeefBeef PorkPork Bacon/SausageBacon/Sausage FishFish PeachesPeaches Peas/BeansPeas/Beans Raspberries/ StrawberriesRaspberries/ Strawberries

Months at –10FMonths at –10F 1515 11 88 55 22 22 33 33 1.51.5

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Use of Food Ingredients

Some ingredients are used in foods to increase Some ingredients are used in foods to increase their shelf-life.All are aimed either at controlling their shelf-life.All are aimed either at controlling microbial growth or preventing fat rancidity.microbial growth or preventing fat rancidity.

Salt tends to reduce bacterial proliferation (Salted Salt tends to reduce bacterial proliferation (Salted pork in the Revolutionary War).pork in the Revolutionary War).

Sodium Nitrite used in cured meats prevents Sodium Nitrite used in cured meats prevents Clostridium botulinum and is a great antioxidant.Clostridium botulinum and is a great antioxidant.

Antioxidants are used to prevent fat rancidity.Antioxidants are used to prevent fat rancidity. Sodium lactate, paraben and other antimicrobial Sodium lactate, paraben and other antimicrobial

agents are used to control bacteria.agents are used to control bacteria.

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Control of Water Activity

Water activity is a measurement of the water that is free Water activity is a measurement of the water that is free to use by bacteria.to use by bacteria.

The goal of using water activity as a preservative The goal of using water activity as a preservative method is controlling bacteria.method is controlling bacteria.

Beef jerky, cheeses and raisins are classical examples.Beef jerky, cheeses and raisins are classical examples. Honey and jellies are also good examples. Although Honey and jellies are also good examples. Although

they contain enough moisture to foster microbial they contain enough moisture to foster microbial proliferation, the water is bond by the high sugar proliferation, the water is bond by the high sugar content.content.

Bakery items and cereals have a very low moisture Bakery items and cereals have a very low moisture content and therefore do not spoil by bacteria.content and therefore do not spoil by bacteria.

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WATER ACTIVITY Aw/ MicroorganismAw/ Microorganism1.0-0.95 Bacteria1.0-0.95 Bacteria

0.95-0.91 Bacteria0.95-0.91 Bacteria

0.91-0.87 Yeasts0.91-0.87 Yeasts

0.87-0.80 Molds0.87-0.80 Molds

0.30-0.20 No microorganism 0.30-0.20 No microorganism proliferationproliferation

FoodsFoodsMeat, fish, sausage, milkMeat, fish, sausage, milk

Cheese, cured meat (ham), fruit juice Cheese, cured meat (ham), fruit juice concconc

Fermented sausages (salami), dry Fermented sausages (salami), dry cheeses, margarinecheeses, margarine

Juice conc, syrups, flour, fruit cakes, Juice conc, syrups, flour, fruit cakes, honey, jellies, preserveshoney, jellies, preserves

Cookies, crackers, bread crustsCookies, crackers, bread crusts

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Control of pH

pH is the degree of acidity. 7=neutral; pH is the degree of acidity. 7=neutral; Below 7 is acid.Below 7 is acid.

Acid foods (below pH=4.6) do not foster Acid foods (below pH=4.6) do not foster spoilage or pathogenic bacterial growth.spoilage or pathogenic bacterial growth.

Fermented items like sauerkraut, pepperoni, Fermented items like sauerkraut, pepperoni, pickles, olives, and other acidified foods are pickles, olives, and other acidified foods are good examples of this method of good examples of this method of preservation. preservation.

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Packaging

Packaging is a relatively new invention.Packaging is a relatively new invention. Packaging can range from a film overwrap (dust Packaging can range from a film overwrap (dust

cover) to oxygen impermeable film to cans and cover) to oxygen impermeable film to cans and jars.jars.

In its simplest form, it acts as a dust cover to In its simplest form, it acts as a dust cover to prevent the reintroduction of dirt, dust etc.prevent the reintroduction of dirt, dust etc.

In its most complex form, the can, it acts also as a In its most complex form, the can, it acts also as a dust cover but also prevents the introduction of dust cover but also prevents the introduction of oxygen and it sturdy to take abuse and still oxygen and it sturdy to take abuse and still maintain its function.maintain its function.

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Packaging

The advent of the oxygen impermeable film has The advent of the oxygen impermeable film has dramatically increased the shelf life of foods from dramatically increased the shelf life of foods from cured meats to potato chips. This film prevents cured meats to potato chips. This film prevents oxygen from getting to the product hence reducing oxygen from getting to the product hence reducing aerobic bacterial growth and retarding fat rancidity.aerobic bacterial growth and retarding fat rancidity.

Some products are now packaged in a modified gas Some products are now packaged in a modified gas atmosphere usually containing nitrogen that is based atmosphere usually containing nitrogen that is based on the exclusion of oxygen but also helps the food on the exclusion of oxygen but also helps the food product from being crushed (e.g. potato chips).product from being crushed (e.g. potato chips).

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New Methods of Food Preservation

Irradiation is now being used to preserve some Irradiation is now being used to preserve some foods. foods.

Spices generally have very high bacteria counts Spices generally have very high bacteria counts and are often irradiated to reduce the bacterial and are often irradiated to reduce the bacterial numbers.numbers.

Potatoes destined for long term storage are often Potatoes destined for long term storage are often irradiated to keep them from spouting.irradiated to keep them from spouting.

Raw meats are now approved for irradiation Raw meats are now approved for irradiation mainly as a pasteurization method for the control mainly as a pasteurization method for the control of pathogenic bacteria.of pathogenic bacteria.

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Food Preservation Combinations

Most foods that you buy use a combination Most foods that you buy use a combination of methods that we just discussed.of methods that we just discussed.

Let’s examine a few foods to see how they Let’s examine a few foods to see how they are preserved.are preserved.

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Potato Chips

They are processed with salt (a pro-oxidant), cooked in They are processed with salt (a pro-oxidant), cooked in oil, which gives them a high, unstable fat content. oil, which gives them a high, unstable fat content. These factors will cause potato chips to go rancid rather These factors will cause potato chips to go rancid rather quickly.quickly.

But potato chips are low in moisture and therefore not a But potato chips are low in moisture and therefore not a good bacterial growth media in addition to being good bacterial growth media in addition to being cooked which kills bacteria.cooked which kills bacteria.

They have antioxidants in them to slow down rancidity.They have antioxidants in them to slow down rancidity. They are packaged in an oxygen impermeable film with They are packaged in an oxygen impermeable film with

nitrogen gas atmosphere thereby preventing rancidity.nitrogen gas atmosphere thereby preventing rancidity.

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Cured Meats

Meat items such as bologna, weiners and ham are high Meat items such as bologna, weiners and ham are high moisture, high fat/ high salt and cooked. Ideal for fat moisture, high fat/ high salt and cooked. Ideal for fat rancidity and bacterial growth.rancidity and bacterial growth.

But they are cooked which pasteurizes them.But they are cooked which pasteurizes them. They are refrigerated to retard bacterial growthThey are refrigerated to retard bacterial growth The salt which promotes fat rancidity also keeps down The salt which promotes fat rancidity also keeps down

bacteria.bacteria. Nitrite (cure) prevents growth of some pathogens and Nitrite (cure) prevents growth of some pathogens and

also is one of the best antioxidants.also is one of the best antioxidants. They are vacuum packaged for bacterial and rancidity They are vacuum packaged for bacterial and rancidity

control (based on the exclusion of oxygen).control (based on the exclusion of oxygen).

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Canned/ Jars of Soups, Fruits and Vegetables

Most of them are heat sterilized to kill all Most of them are heat sterilized to kill all bacteria.bacteria.

When processed in the jar or can, oxygen is When processed in the jar or can, oxygen is evacuated before sealing to prevent fat evacuated before sealing to prevent fat rancidity.rancidity.

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Milk and Dairy Products

Most dairy products are pasteurized which Most dairy products are pasteurized which is a heat-based treatment to reduce bacteria.is a heat-based treatment to reduce bacteria.

Sold as refrigerated item. Controls bacterial Sold as refrigerated item. Controls bacterial via cold methods.via cold methods.

Are usually packaged to remove oxygen to Are usually packaged to remove oxygen to prevent fat rancidity.prevent fat rancidity.

Items such as cheeses have a low pH and Items such as cheeses have a low pH and water content for extended shelflife.water content for extended shelflife.

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Cereal and Bakery Items

Bacteria is not usually a problem because of Bacteria is not usually a problem because of low moisture content.low moisture content.

Fat rancidity is not a big problem because Fat rancidity is not a big problem because they are fairly low in fat and some they are fairly low in fat and some antioxidants are usually added.antioxidants are usually added.

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Fresh Fruits and Vegetables

Shelf-life is usually several weeks.Shelf-life is usually several weeks. Some fruits and vegetables are irradiated or Some fruits and vegetables are irradiated or

packaged in modified gas atmospheres to packaged in modified gas atmospheres to control the ripening process and retard control the ripening process and retard microbial growth.microbial growth.

Fat rancidity is not a problem-little or no Fat rancidity is not a problem-little or no fat.fat.

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Conclusions

Food preservation has had a long history and has Food preservation has had a long history and has only more recently been scientifically understood.only more recently been scientifically understood.

An understanding of the fundamentals of food An understanding of the fundamentals of food preservation and the conditions affecting bacterial preservation and the conditions affecting bacterial growth (FAT TOM) has helped to develop newer growth (FAT TOM) has helped to develop newer and more technologically advance methods of and more technologically advance methods of food preservation.food preservation.