Lipolysis and oxidative stability of soft ripened cheeses containing vegetable oils

Abstract

In response to nutrition guidelines recommending a reduction in saturated fats in human diets, the dairy industry has developed new products containing unsaturated fats to satisfy the demand of the more health conscious consumer. The fatty acid composition of milk, naturally rich in saturated fatty acids (SFA), can be modified either through genetic selection of dairy cows or by changing feed composition (Palmquist et al. 1993). For example, a number of dairy products including butter (Wood et al. 1975; Badings et al. 1976), Gouda (Badings et al. 1976) and Cheddar (Wong et al. 1973; Lightfield et al. 1993) containing increased amounts of linoleic acid (18[ratio ]2n–6) have been made from the milk of cows given diets supplemented with unsaturated lipids. However, dairy farmers would prefer to produce milk as cheaply as possible, leaving it to food technologists to modify milk components at the post- production stage (Banks, 1987). Therefore, dairy products made from skim milk combined with a fat mixture could be attractive, but little information is available on this type of modified product. One major problem related to the introduction of unsaturated fats into dairy products is the possible alteration of their properties. Indeed, Badings (1970) reported that butter enriched in polyunsaturated fatty acids (PUFA) has reduced flavour quality and shelf life. It is well known that PUFA are easily oxidized and can form undesirable compounds such as peroxides and aldehydes. Moreover, PUFA are more likely to be oxidized as free fatty acids (FFA) than to be integrated into a triacylglycerol structure. Therefore, when a dairy product is made by recombining skim milk with unsaturated fats, such as the soft ripened cheese in this study, it is important to consider both lipolysis and oxidative stability of the lipid fraction. This was our objective in this study.