Capillary electrophoresis and Western blotting detection of ovine and caprine cheese whey added to bovine milk

The detection of the fraudulent addition of ovine and caprine rennet wheys to unheated and heated bovine milk was carried out by capillary electrophoresis (CE) analyses of ovine and caprine caseinomacropeptides (CMP) and immunoblotting, following isoelectric focusing (IEF), to distinguish between P-lactoglobulins (beta -Lg) from the 3 species. CE of deproteinized milk fractions soluble at pH 4.6 allowed the detection of 1% (vol/vol) added whey, and heat treatment of the adulterated milk only caused a 10-20% decrease in the areas of the ovine and caprine CMP peaks. However, an accurate quantitative determination could be restricted by the presence in bovine milk of a component with a migration time similar to that of ovine and caprine CMPs. The immunoblots of IEF of the fractions soluble at pH 4.6 of adulterated unheated bovine milks revealed the presence of ovine and caprine beta -Lgs, showing that detection of additions of 0.5% (vol/vol) of ovine and caprine wheys was possible. In milks submitted to a heat treatment equivalent to an UHT process, the detection levels were 1% and 2.5% (vol/vol) of ovine and caprine whey, respectively.