Methods for detection of soymilk adulteration in milk.

Abstract

Methods for detection of adulteration in milk with soymilk have been described. The methods are based on (i) differences in optical activity of sugars present in bovine milk vis-à-vis soymilk (polarimetric method), (ii) the differences in isoelectric point of major milk proteins vis-à-vis soy proteins (isoelectric precipitation method), (iii) differences in molecular weights of proteins present in bovine milk vis-à-vis soymilk (SDS-PAGE method), and (iv) the reactivity of soy protein antiserum towards adulterated milk (immunodiffusion method). The adulteration detection limits of immunodiffusion, SDS-PAGE, isoelectric precipitation and polarimetric methods were at levels of 1, 5, 5-10 and 10%, respectively. Although, immunodiffusion method required soy-specific antiserum, the method is sensitive as well as reliable. SDS-PAGE and immunodiffusion methods are not prone to interferences by other adulterants viz., sugars, and neutralizers. These methods can be adapted in quality control labs for checking adulteration in milk with soymilk.