Rancidity in Indian butterfats (ghee).

It has long been realized that the analytical characteristics of deteriorated butterfats depart considerably from those of the fresh fats. It is the more surprising, therefore, that the changes in butterfat, or ghee, during ordinary rancidificationin loosely corked containers exposed to diffused daylight-have not been more intensively studied. Elsdon, Taylor & Smith (1931) studied commercial butters for very short periods and found increased Polenske values, while for butterfat Godbole & Sadgopal (1936) found decreased Polenske and increased Reichert values. Curli (1939) and Das Gupta (1939) excluded air from their samples during storage, while Narasimhamurty (1941) used commercial ghee samples whose purity was open to suspicion. In the present study, sets of samples of genuine butterfat from three different localities were chosen, and stored under the first-mentioned, more or less 'normal' conditions. The samples were not chosen at random, but represent characteristic products, one group from Indian buffaloes the butterfats ofwhich were ofroughly normal Reichert value (high for a buffalo) and normal iodine value, another from buffaloes heavily fed with cottonseed, a practice common in many dry areas in India, and a third from cows in pasture, such as are produced in any well-kept dairy. It is possible, therefore, to draw comparisons between one set and another and also between individuals in the same group, a feature which will be appreciated during the discussion. , A study of the changes in the characteristics alone, while it enables certain conclusions to be drawn, would it was felt be somewhat restricted and it was decided therefore to isolate and study the free fatty acids produced by rancidity in the three batches of ghee. The products of spoilage of fats, as hitherto enumerated and sometinles isolated, include inter alia ketones, aldehydes, peroxides, hydroperoxides, ozonides, hydroxyacids and fatty acids. Whilst clearly the terms rancidity and acidity due to free fatty acids are not equivalent, it will be conceded that free fatty acids, especially over long periods as in the present instances, certainly form the largest proportion of the rancidity products, and may amount to as much as 20 % of the rancid fat, while peroxides (calculated as oleic peroxide) may approach only 2 % and aldehydes and ketones, according to Mundinger (1930), 'can be detected'.