GHEE BOILING

MOKSHA CHIB 13FET1003

GHEE

Codex Alimentarius: Ghee is a pure clarified fat exclusively obtained from milk, cream or butter by means of processes involving application of heat at atmospheric pressure, which result in almost total removal of water and non-fat solids, with an especially developed flavor and physical structure and texture.

• India utilises 28% of milk produced for the manufacture of ghee, & in 2002, it was estimated that the annual production figure was 900000tonnes, which was valued at 135000 million INR

• It is considered as a supreme cooking or frying medium

PARAMETER COW BUFFALO

RM value 16.9-29.7 14.5-39.9

Polenske value 0.9-3.2 0.4-5.3

Iodine value 31.0-45.6 21.4-39.9

Butyro-refractometer reading (40˚C)

42.5-47.7 40.9-46.9

Melting point (˚C) 28.8-35.7 26.6-36.1

Unsaponifiable matter (g/100g) 0.42-0.49 0.45-0.54

Saponification value 212.8-232.8 198.0-239.3

Kirschner value 22.1 28.4

Softening point (˚C) 33.5-33.9 33.5-34.6

Smoking point (˚C) 252.0 Not reported

GHEE MANUFACTURE

Preparation of butter, cream or makkhan followed by heat

desiccation

To convert butter to ghee, heat is applied at controlled temps. At the various stages of processing

I. Temp raised to about the bpt. of water while stirring to control frothingII. Most of the free water evaporates, the rate of heating is controlled & the

temp. is maintained at about 103˚C to prevent charring of SNF, which might result in the development of bitter flavors & brown colors

III. Temp. raised to about 105-118˚C with constant agitation to remove the water bound to SNF & to develop characteristic flavor. A temp range of 110-120 ˚C is preferred

A lower heating temp. improves the color but decreases the keeping quality of ghee due to greater moisture content. A higher temp. on the other hand, tends to reduce Vitamin A content & darken the color, but increases the keeping quality of the finished product.

INDIGENOUS MILK BUTTER (MB) METHOD

• Involves souring of raw milk in earthenware vessels, which contain bacteria within the walls of the container

Direct churning of raw milk

• Dahi is churned to make makkhan• Wooden beaters are used to separate makkhan, which is then

melted till all the moisture is removed

Lactic acid fermentation of heat-treated milk to

dahi followed by churning

• Initially, excessive frothing takes place which must be controlled to prevent boil-over till moisture evaporates, frothing subsides & temp reaches 100 ˚C

• At this temp, caramelization of curd particles is noticed & heating is discontinued as curd particles attain golden yellow color. Contents are left undisturbed till the residues settle down. Clarified fat is decanted off.

Skimming of clotted cream layers

(malai)

This method leaves a large quantity of ghee residue & also leads to low fat recoveries (88-90%).

CREAMERY BUTTER (CB) METHOD Cream is

separated from raw milk

Cream is churned into

butterButter is

melted to 60 ˚C, pumped into heating

kettle & steam pr. ↑ed to

raise the temp. to 90 ˚C

Contents are constantly agitated to

prevent scorching

‘Scum’ collected on

the top surface is removed

from time to time

When all moisture has

been removed, temp. shoots

up & heating is carefully

controlledAt the end point, a characteristic

ghee flavor emanates indicating

sufficient heat treatment (110-

120 ˚C)

Ghee is then pumped, via an

oil filter/clarifier, into settling

tanks, cooled by circulating

water at 60 ˚C Product is

transferred for packaging & granulation

• There is profuse effervescence accompanied by crackling sound initially, but both gradually decrease as moisture content is reduced

• End point shows the disappearance of effervescence, appearance of finer air bubbles on the surface of the fat & browning of the curd particles

• A fat recovery of 88-92% has been reported

DIRECT CREAM (DC) METHOD • This method omits the need for production of butter because cream is directly converted into ghee

• The fresh cream obtained by centrifugal separation of whole milk, cultured cream or washed cream is heated to 115 ˚C in a stainless steel, jacketed ghee kettle fitted with an agitator, steam control valve, pressure and temperature gauges and a movable, hollow, stainless steel tube centrally bored for emptying out the contents

• Heating is discontinued as soon as the color of the ghee residue turns to golden yellow or light brown. The ghee residue is used for animal feeding

LIMITATIONS

• It requires long heating time to remove the moisture • Ghee produced has a slightly greasy nature• A high content of serum solids in cream may also produce a

highly caramelized flavor in ghee & lead to about 4-6g/100g loss of butter fat in ghee residue, depending on the fat %age in the cream

PRE-STRATIFICATION (PS) METHOD Also known as clarified butter, induced- stratification or the stratification method, takes advantage of gravity settling for removing most of the moisture from butter & saves the large thermal energy required for removing moisture otherwise.

Method involves melting of butter mass at 80-85 ˚C, pumping the mass into a vertical storage tank and then leaving it undisturbed for 30 min. During this method, butter stratifies into three distinct layers :

CURDY MASS

FATBUTTERMILK SERUM

BUTTERMILK SERUM: Consists of about 80g/100g of the moisture & 70g/100g of the SNF contained in butter. It is drained off from the bottom of the vat. This removal eliminates the need for prolonged heating for evaporation of moisture & results in formation of a significantly low quantity of ghee residue, thereby reducing the fat losses.

FAT: The fat layer is drawn into a double-jacketed steam kettle where it is heated to 105-110 ˚C to evaporate any traces of moisture and for developing the typical ghee flavor.

PS method has been reported to save time and labor up to 45%, gives a slightly higher ghee yield than direct clarification; the product is lower in moisture, FFA and acidity & less susceptible to peroxide development during storage, produces ghee with mild flavor.

BENEFITS1. Only small hold-up of raw material

in the plant at any time and hence no chance for whole batch being spoiled

2. High heat transfer coefficient, compact design

3. Easy capacity control with no foaming problem

4. Short residence time & less heat damage to the product

5. System is adaptable to automation & CIP

6. Better economic operation7. Minimum strain on operator8. Improved flow characteristics of

the product

CONTINUOUS GHEE MAKING Overcomes the problems of batch methods of ghee making, such as limitations of scale of operation and excessive exposure of the plant operators to the stress of heat & humidity

METHOD I

Molten butter is pumped through successive stages

of scraped surface HE

Ghee leaving the final stage is

passed through a centrifugal

clarifier to remove residue

Clarified ghee is stored in a tank for final packaging

Fat is concentr

ated

Fat-in-water emulsion is

mechanically broken with the

help of centrifugal force in clarifixator

Heat is supplied till the

development of flavor & removal

traces of moisture

METHOD II

CHEMICAL COMPOSITION OF GHEECONSTITUENT (g/100g) BUFFALO COW

Saponifiable constituentsFatMoistureSaturated fatCis-MonoeneTrans-MonoeneDienePolyene

99.0-99.5< 0.546297135

99.0-99.5< 0.5NANANANANA

TriglyceridesShort chainLong chainTrisaturated High meltingUnsaturated

43-4954.732-476-1256

36-4062.432-423-754.5

Partial glyceridesDiglyceridesMonoglyceridesPhosphoglycerides (mg/100g)

4.50.642.5

4.30.738.0

CONSTITUENT BUFFALO COW

Unsaponifiable constituents Total cholesterol (mg/100g)Lanosterol (mg/100g)Lutein (µg/g)Squalene (µg/g)Carotene (µg/g)Vitamin A (µg/g)Vitamin E (µg/g)Ubiquinone (µg/g)

275.08.273.162.40.09.526.46.5

330.09.324.259.27.29.230.55.0

Flavor compoundsTotal free fatty acids (mg/g)Headspace carbonyls (µM/g)Volatile carbonyls (µM/g)Total carbonyls (µM/g)Total lactones (µg/g)

5.83-7.580.0270.268.6435.4

5.99-12.290.0350.337.2030.30

FLAVOUR COMPOSITION: CARBONYLS Both monocarbonyls & dicarbonyls have been identified in ghee. The quantity of carbonyl was found to be directly proportional to the temperature of clarification.

• On storage, no new carbonyls were detected but there was a marked increase in the alkanals, alk-2-enals & alk-2,4-dienals, which may be a reason for deterioration In ghee flavor during storage

• In about 100 days of storage at 37 ˚C, an off-flavor developed with a significant 4- to 5- fold rise in gas-stripped carbonyls. After 200 days, all ghee samples developed pronounced off-flavors, & levels of carbonyls increased 9- to 10-fold (Gaba & Jain, 1976)

• The desi ghee made from buffalo's milk contains significantly higher concentrations of carbonyl compounds, and has a better flavor than ghee made under controlled conditions, probably due to flavor contributed by the adventitious microorganisms getting entry through contamination

HEADSPACE CARBONYL

% OF TOTAL

COW GHEE

BUFFALO GHEE

Alkan-2-ones 85 79

Alkanals 11 19

Alk-2-enals 2 1

Alk-2,4-dienals 2 1

FLAVOUR COMPOSITION: LACTONES

PROPERTIES

Components δ-lactone: 85-90%γ-lactone: 5-10%

Ratio of δ-lactone to γ-lactone

6:1 – 20:1

Saturation Saturated lactones: 65%Unsaturated lactones: 35%

Flavor Pleasant flavor but variations may result in off-

flavor

Lactones have a coconut-like aroma, which is associated with the characteristic flavor of ghee.

• Levels of γ-lactones & δ-lactones and total lactones are reported to be higher in buffalo ghee than on cow ghee

• Lactone levels were higher in ghee prepared by DC method than that prepared by the creamery or desi method

•It is only one component of ghee flavor, others namely FFAs and carbonyls are more dominant

•Lactone level is found to increase with clarification which showed that heat plays a important role in the formation of lactones

FLAVOUR COMPOSITION: FFAs & ESTERS

FREE FATTY ACIDS

• FFAs are responsible for rancid flavor & also contribute to the normal flavor of ghee, and their level has been closely related to the flavor quality

• The lower fatty acids C6:0-C10:0 though present in low conc. in ghee accounting fro only 5-10% of total FFA, contribute significantly to ghee flavor

• Conc. of both medium-chain (C10:0 to C14:0) and long-chain (C15:0 and above) FFA were higher in cow ghee than in buffalo ghee

• Ripening of cream affects the concentration of FFA in ghee, being higher in the product prepared from ripened than from unripened cream or butter

ESTERS

• Esters may originate from the esterification of short-chain alcohols and FFA by the action of bacterial esterases & are powerful odor compounds contributing to the flavor of ghee

FLAVOUR FORMATION The heating process generates flavor compounds through the interaction of lipids, protein degradation products, lactose, minerals and metabolites of microbial fermentation.

FLAVOUR FORMATION

I. CARBONYL COMPOUNDS: They are formed as a result of microbial metabolism of various milk constituents, oxidation of milk lipids, heat decomposition of milk carbohydrates and fat. When ghee is made from fermented milk or cream, acid carbonyl compounds are expected to form through complex reactions between some carbonyls, such as glyoxal and methylglyoxal with amino acids

II. Products like ketoglycerides & carbonylic compounds are formed from oxidation of lipids whereas polar (dicarbonyl) compounds, such as diacetyl, furfural and hydroxymethylfurfural are formed by dehydration & thermal degradation of carbohydrates

III. Production of flavor also depends on the extent to which the flavoring metabolites, such as FFA & carbonyls are transferred from the aqueous to the fat phase during heat clarification as a result of moisture removal. When the water is evaporated, the flavor compounds that are water soluble but have higher boiling points than water remain in the fat phase. In addition, the steam volatile monocarbonyls are more intimately associated with the fat phase than with the water phase

THERMAL OXIDATION Since 80% of the ghee produced in India is used for culinary purposes (i.e. for frying), the changes taking place in the composition of ghee during heating at different temperatures are of great interest.

PARAMETER EFFECT Effect on saponifiable

matter• Prolonged heating of ghee at temperatures ranging from 150-225◦C for 2 h results in gradual ↓ in triglycerides and an ↑in di- & mono-glycerides, probably due to hydrolysis• Heating of ghee up to 225◦C has no appreciable effect on saturated fatty acids from C4:0 to C12:0, but causes a decrease in C10:1, C14:1, C16:1, C18:1, C18:2 and C18:3 fatty acids• The higher the temp, the greater is the effect

Effect on unsaponifiable constituents

• Prolonged heating ↓the cholesterol, carotene, vitamin A and E contents of ghee• At 200◦C and 225◦C of heating, carotene and vitamin A were destroyed completelywithin 15 min, but the losses in vitamin E were 65.5 and 71.0%• Vitamin E was completely destroyed at the end of a 30-min heating period

Effect on carbonyl compounds & flavor

• Upon heating fresh ghee at 150◦C, peroxides and epoxides ↑ with ↑ing heating period• Thermally oxidized ghee contains more peroxides of lower polarity than of higher polarity• A great ↑ in the ratio of monocarbonyls to total carbonyls with saturated aldehydes as main monocarbonyls were reported

Effect on physicochemical properties

• Prolonged heating does not appreciably change the RM, Polenske and saponification values, but slightly ↑the FFA content and butyro-refractometer reading and ↓ the iodine value of ghee when heated at 150–225◦C for 2 h• The higher the temp and greater the period of heating, the greater is the effect