Cholesterol and Antioxidant Vitamins in Fat Fraction of Whole and Skimmed Dairy Products

Abstract

The skimming procedure is a common practice in dairy industry, and skimmed products contain less fat, less cholesterol and less fat-soluble vitamins than whole products. The aim of this research is to verify if something else happens during the skimming process to these compounds in milk and dairy products. Experimental milk and cream samples, ranging from 0.1 to 51.5 g fat/100 g, have been studied for beta carotene, alfa-tocopherol and cholesterol contents. The degree of antioxidant protection (DAP), useful to estimate the potential oxidative stability of fat in foods, has been calculated, combining these values. The same analytical protocol has been also applied to commercial products (fat content ranging from 0.1 to 85.0 g/100 g). As was expected, there is a good linear correlation between these compounds and fat content in experimental and in commercial samples; nevertheless, the composition of milk fat changes differently. During skimming process, in the residual fat matter, cholesterol concentration increases while antioxidant compound concentration decreases or remains unchanged. Moreover, in experimental and in commercial milk and dairy, the DAP values show that the residual cholesterol is more susceptible to oxidation in skimmed than in whole products. This aspect is particularly important from a safety point of view: actually, cholesterol oxide ingestion can be harmful and should be avoided even in a small amount.