Prevention of Hydrolytic Rancidity

Sufficient knowledge exists to enable dairy industry personnel to take precautions to ensure a low incidence of hydrolytic rancidity and associated problems in milk and milk products. Recommendations for prevention have been published (Deeth and Fitz-Gerald, 1976 IDF, 1991 O Brien et al., 1996). A summary of these is given below. 

Hygiene on the farm and in the factory is of paramount importance in controlling microbial growth and minimising lipolysis problems. Inadequately cleaned equipment can be a major source of lipolytic psychro-trophic contaminants (Drew and Manners, 1985 Stead, 1987). 

It has been suggested that some form of heat treatment, either thermi-zation (Humbert et al., 1985 Matselis and Roussis, 1998) or HTST pasteurization (Mogensen and Jansen, 1986), of milk on arrival at the factory should be performed to minimise the incidence or reduce the severity of lipolysis problems. While such treatments have been shown to be effective, they increase the cost of processing and result in double heat treatment of milk, which is not permitted in some countries. Carbonation of raw milk (with 30 mM C02) has also been reported to reduce the growth of lipolytic psychrotrophs and also to reduce the level of FFAs in cheese made from the carbonated milk (McCarney et al., 1994). 

Once lipolysis has occurred there is little that can be done to reduce its effects on quality, although, in laboratory trials, Nakai (1983) successfully removed FFAs from rancid milk by adsorbing them on activated charcoal and Takacs et al. (1989) by the use of a C18 column. However, such nonspecific adsorption methods are unlikely to find widespread use as other milk components such as proteins and vitamins are also removed. 

Purification and partial characterization of psychrotrophic Serratia mar-cescens lipase. 1. Dairy Sci. 86, 127-132. 

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Ramezanzadeh, F, Rao, R, Windhauser, M, Prinyawiwatkul, W, Tulley, R and Marshall, W (1999) Prevention of hydrolytic rancidity in rice bran during storage. J. Agric. Food Chem., 47, 3050-3052. 

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