Lipolytic rancidity

Fats deteriorate in two ways. One is normally a chemical process the other is normally enzymatic. They are oxidative rancidity and lipolytic rancidity. In the former, oxygen (normally in the form of a free radical) adds across double bonds. As this is a zero activation energy process it is... 

This specification is for butter oil, which is butter with the water removed. The free fatty acid limit is to detect lipolytic rancidity while peroxide value specification is to limit oxidative rancidity. The copper limit arises because copper catalyses the oxidation of fats. The absence of neutralising substances is to prevent a high titration for free fatty acids being covered up by the addition of alkali. 

McNeill, G.P., O Donoghue, A., Connolly, J.F. 1986. Quantification and identification of flavor components leading to lipolytic rancidity in stored butter. Irish J. Food Sci. Technol. 10, 1-10. 

Nakai, S., Perrin, J.J., Wright, V. 1970. Simple test for lipolytic rancidity in milk. J. Dairy Sci. 53, 537-540. 

There are two processes that cause fats to deteriorate. One is normally a chemical process (oxidative rancidity), the other normally enzymatic (lipolytic rancidity). 

Lipolytic rancidity is normally enzymatic, the enzymes responsible usually coming from bacteria or moulds. The effect of lipolytic rancidity is that the level of free fatty acid rises. The effect of this on the product depends very much upon the nature of the free fatty acid liberated. Low levels of free butyric acid from milk fat tend to enhance a toffee by giving it a more buttery flavour, whereas lipolysis of a lauric fat such as HPKO gives free lauric acid, which is an ingredient of, and tastes of, soap. This effect is very unpleasant. 

An increasing problem is lipolysis in butter fat after manufacturing, which is caused by thermoresistant hpase enzymes that are created in the milk or cream by psycho-trophic bacteria or by residual native lipases that sirrvive pasteurization. Based on a determination of the lipase activity in cream, the keeping quality of manufactured butter in regard to hpolysis can be predicted with reasonable accirracy. A similar prediction for sweet cream butter can be based on lipase activity in the serum phase (71). The characteristic lipolytic flavors that can develop in milk products are primarily associated with the short- and medium-chain fatty acids that are relatively abundant in milkfat they have lower flavor threshold values than the long-chain fatty acids. As a result of improvements in the quality of raw milk and the standards of processing, lipolytic rancidity is seldom present in the fat source before its use in recombination (72). 

Deeth, H.C. and Fitz-Gerald, C.H. (1995) Lipolytic enzymes and hydrolytic rancidity in milk and milk products, in Advanced Dairy Chemistry, Vol. 2 Lipids, 2nd edn (ed. P.F. Fox), Chapman Hall, London, pp. 247-308. 

Parmesan or Grana, as it is known in Italy, is a group of very hard bacteria-ripened, granular-textured cheeses made from partially skimmed cow s milk. They originated in Parma, near Emilia, Italy, hence the name. Special lipolytic enzymes derived from animals are used, in addition to rennet, to produce the characteristic rancid flavor. 

Bovine blood serum is lipolytically active, but cows producing milk which goes rancid quickly do not have sera that are more lipolytically active than those producing normal milk. Leukocytes, which are present in large numbers in milk, are especially high in mastitic milk they are the source of milk catalase but are apparently not the source of milk lipases (Nelson and Jezeski 1955). 

Law, B. A., Sharpe, M. E. and Chapman, H. R. 1976C. The effect of lipolytic gramnegative psychrotrophs in stored milk on the development of rancidity in Cheddar cheese. J. Dairy Res. 43, 459-468. 

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