Electrophoretic Distinction of the Origin in Different Dairy Products and Milk Samples

Caseins, lacto-albumin, and lacto-globulin are major milk proteins. These globular proteins could be significant indicators of the milk and dairy products origin. Knowing that caseins, lacto-albumins and lacto-globulins vary in molecular weight and concentration in different types of milk, this fluctuation can be used for determination of milk origin. The aim of this study was to develop an appropriate method for distinction of milk proteins from different origin. Twelve samples of milk, white cheese, yellow cheese and whey cheese from cow, sheep and goat were obtained and studied. The protein separation was made using SDS-PAGE. SDS is an anionic detergent that breaks all inter and intramolecular bonds and leaves the polypeptide subunits of proteins in forms that can be separated on the basis of their molecular weight. Polyacrylamide gels, used as support medium, restrain larger molecules from migrating as fast as smaller molecules. In order to optimize the conditions of the experiment, some of the parameters were modified (polyacrilamide concentration from 10-15% according to the molecules size, duration of electrophoresis, quantity of applied material, sonification treatment of the different samples). Bovine milk proteins standards were used for the determination of the proteins. The results have shown differences, as well as other fractions that can be used for identification of the origin. In yellow and white cheese the differences among the samples from different origins appear in lacto-albumin fractions and some digested fractions below the caseins. The main differences in whey cheese samples were identified in casein fractions. The milk samples showed differences in upper fractions, probably serum albumins that remained in the milk samples