Factors Affecting Composition and Analytical constants of Ghee

Ghee, as defined earlier, is a pure heat clarified butterfat. In broad chemical definition, milk fat is referred to as triglyceride of fatty acids, containing varying quantities of other substances. Milk fat contains about 500 fatty acids and fatty acid derivatives with 4 to 20 or more carbon atoms in their chain. The fatty acids usually contain an even number of carbon atoms, but they may be saturated or unsaturated.Nearly 80% of the cow and buffalo milk fats consists of only five fatty acids,namely palmatic, oleic, stearic, myristic and butyric. The polyunsaturated fatty acids of butterfat constitute about 3%.

The fatty acid composition of milk fat greatly influences the fat constants and rheological properties, such as melting and crystallization behaviour, that affect the texture of ghee. These fatty acids as such and by interaction with other milk constituents also influence the flavour of ghee. Excess amount of long chain saturated fatty acids, like palmatic and stearic acid and thus substantially high amount of high melting triglycerides make the ghee hard and develops good grains. The high proportion of low carbon atom saturated acids, for example, butyric and caproic acids and polyunsaturated fatty acids make the ghee softer with poor granularity.The more prominent of the above factors that affect the lipid profile of milk fat and eventually the composition and analytical constants of ghee are discussed as below:

Effect of Species: The quality of ghee from cow milk and buffalo milk is different particularly in terms of colour and texture. This difference is attributed to the fatty acid profile and other constitutes of the two species, which are different. For example, yellow colour in cow ghee is due to carotene, which is absent in buffalo milk. The fatty acid composition of cow milk and buffalo milk fat is shown in the table
Fatty acid composition of cow and buffalo milk fat
Fatty acid composition of cow and buffalo milk fat
Since the long chain saturated fatty acids like palmatic and stearic are more in buffalo butterfat, buffalo ghee is harder with bigger grains than cow ghee. The other analytical constants of the cow ghee and buffalo ghee (table) are also different because of variance in their fatty acid composition.Effect of Feed: The bulk constituents of the feed of ruminant milch animals are crude fibre, protein and fat, which together make up the total digestible nutrients.These are required not merely for maintenance of animal body but as a raw material for production of the constituents of milk.

(a) Proteins in the diet are the source of milk protein. Normally dietary proteins do not contribute to the synthesis of milk fat.

(b) Fats/oils and their cakes in the diet have most striking effect on the fatty acids composition and the analytical constants. Feeding whole cottonseed oil or cake increases the oleic acid content (and likewise iodine value) by about 10 units and a sharp increase, often to almost double the original values, occurs in stearic acid, bringing it upto even 20%. In compensation the contents of palmatic acid and of lower fatty acids taken as a whole are depressed almost to the same proportion.The dietary groundnut oil, hydrogenated groundnut oil, sesame oil, safflower oil,their seeds or cakes also increase the oleic acid and stearic acid and decrease the palmatic and lower fatty acids. The overall result is that ghee obtained from feeding of these seeds and cakes lower the RM value, polenske value and sponification value and increase of BR reading and iodine value, and such ghee are hard,granular and sometimes even waxy in appearance. Feeding of coconut cake increases lauric acid and myristic acid levels. Rape oil when feed to animal, elevates the oleic acid and depresses the palmatic acid content and thus decreases RM value and increases iodine value.Feeding of carbohydrate materials, such as crude fibre, cellulose, starch and sugar also contribute in the synthesis of butterfat, especially in the built up of lower fatty acids. Feeding of animals on pasture grass or silage or under a regimen of green fodder produces butterfat with high proportion of lower fatty acids, such as butyric and caproic, which result in high RM value and Polenske value. This affect is commonly observed after the monsoon. Excessive feeding of green grass or fodder is stated to yield a soft butter of high iodine value, for which the highly unsaturated fatty acid may be responsible. Feeding large quantities of roots, which are rich in fibre and low in protein, yield butterfat of very low iodine value (about 30) and high RM value and Polenske value.The dietary conditions of the animals also influence carotene, vitamin A and vitamin E constituents. Any carotene present in milk fat is, in fact, of dietary origin, while vitamin A arises either from dietary carotene or from reserves of vitamin A alcohol stored in the liver, which ultimately are also derived from ingested carotene or vitamin A. Hence the level of these materials in diet will influence their amounts secreted in milk fat. Feeding of more oil cakes and lowering of intake of green fodder generally lower the carotene and vitamin A content in butterfat. Similarly the a-tocopherol (also termed as vitamin E) in butterfat is of dietary origin. Therefore,its level is also dependent on the intake through feed.Effect of Season: The season has indirect effect on the fatty acids and analytical constant of butterfat. The feeding regimen changes with the change in season. In monsoon there is more availability of green fodder and pasture feeding practice is also adopted. In the summer months, green fodders are not available, which are replaced by silage, dry straw and fibrous feeds. As discussed above the change in dietary conditions of the animals will alter the fatty acids composition and vitamins of butter fat.

Effect of Method of Preparation of Ghee: Adoption of any method for manufacture of ghee using good quality raw material generally does not alter the fatty acid profile and analytical constants. But the other lower constituents like carotene,vitamin A and E and phospholipids are affected by the method of manufacturing ghee. At each stage of processing during ghee making, such as cream separation,pasteurization, butter making, some loss of carotene and vitamin A takes place,hence more the steps involved in the method of ghee making lesser will be the percentage of these constituents. In case of indigenous method of ghee making higher recovery of vitamin A is achieved because large amount of fat soluble vitamin A is transferred to the fat phase during souring of whole milk into dahi and subsequently during churning of dahi into makkhan. Raising temperature to more than 125oC during manufacture of ghee and storage of ghee for prolonged period drastically reduces the vitamin A content and almost completely destroy carotene content. But, the method of manufacture of ghee has no bearing on the tocopherol content, which is in very close range when prepared by different methods. Also tocopherol in ghee is quite stable to heat. The total phospholipid content of creamery cow butter varies between 75-218 mg/100g, which is higher than the values of 61-67 mg/100 g found in cow makkhan (curd process butter) and 46 mg/100 g in buffalo makkhan. There is no loss of phospholipid on converting butter or makkhan into ghee.

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