αS1-casein in goat milk: identification of genetic variants by Capillary Zone Electrophoresis compared to Isoelectric Focusing

AlphaS1casein fraction in caprine milk is characterized by an important polymorphism due to substitution, deletion of amino acids and post trascriptional modifications (Grosclaudeet al., 1994; Ferrantiet al., 1997). This structural polymorphism is associated to a quantitative variability in protein expression related to different milk quality and dairy properties (Pierreet al., 1998; Remeuf, 1993; Vassalet al., 1994). Classical electrophoretic methods were applied to characterize the phenotypic variants at αS1-casein fraction (Addeoet al., 1988; Russoet al., 1986). During the last ten years capillary electrophoresis became an analytical technique for rapid and automated analysis requiring small sample volume and small solvent waste. These characteristics, together with the high resolution and the chance to give quantitative results, made this technique a useful tool in studying milk protein characterization and in detecting adulteration (Cattaneoet al., 1996a; 1996b) in different application fields. CZE was applied to the study of caprine milk proteins to quantify high, medium and low αS1- casein content and to identify genetic variants αS1A, B and C on the basis of their different migration time (Recioet al., 1997). The aim of this work was to test a CZE procedure able to identify and discriminate the main αS1caprine variants A, B, E and F through specific and repeatable electromigration patterns. Comparison between CZE and IEF assays is discussed.