Ghee boiling

Delve into the detailed production of Ghee from milk and what gives it the characteristic flavor.

1. GHEE BOILING MOKSHA CHIB 13FET1003

2. 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-refractomete r 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

3. GHEE MANUFACTURE To convert butter to ghee, heat is applied at controlled temps. At the various stages of processing Temp raised to about the bpt. o f water while stirring to control frothing 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 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.

4. INDIGENOUS MILK BUTTER (MB) METHOD This method leaves a large quantity of ghee residue & also leads to low fat recoveries (88-90%).

5. CREAMERY BUTTER (CB) METHOD 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

6. 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

7. PRE-STRATIFICATION (PS) METHOD Also known as clarified butter, induced- stratification or the stratification method , takes advantage of g ravity 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 FAT BUTTERMILK 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.

8. BENEFITS Only small hold-up of raw material in the plant at any time and hence no chance for whole batch being spoiled High heat transfer coefficient, compact design Easy capacity control with no foaming problem Short residence time & less heat damage to the product System is adaptable to automation & CIP Better economic operation Minimum strain on operator 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 METHOD II

9. CHEMICAL COMPOSITION OF GHEE CONSTITUENT (g/100g) BUFFALO COW Saponifiable constituents Fat Moisture Saturated fat Cis-Monoene Trans- Monoene Diene Polyene 99.0-99.5 < 0.5 46 29 7 13 5 99.0-99.5 < 0.5 NA NA NA NA NA Triglycerides Short chain Long chain Trisaturated High melting Unsaturated 43-49 54.7 32-47 6-12 56 36-40 62.4 32-42 3-7 54.5 Partial glycerides Diglycerides Monoglycerides Phosphoglycerides (mg/100g) 4.5 0.6 42.5 4.3 0.7 38.0 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) 275.0 8.27 3.1 62.4 0.0 9.5 26.4 6.5 330.0 9.32 4.2 59.2 7.2 9.2 30.5 5.0 Flavor compounds Total free fatty acids (mg/g) Headspace carbonyls (µM/g) Volatile carbonyls (µM/g) Total carbonyls (µM/g) Total lactones (µg/g) 5.83-7.58 0.027 0.26 8.64 35.4 5.99-12.29 0.035 0.33 7.20 30.30

10. 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

11. FLAVOUR COMPOSI TION : 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

12. FLAVOUR COMPOSI TION : 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

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

14. FLAVOUR FORMATION 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, a cid carbonyl compounds are expected to form through complex reactions between some carbonyls, such as glyoxal and methylglyoxal with amino acids 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 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

15. 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 completely within 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