Detection of cow's milk in Shaanxi goat's milk with an ELISA assay

The aim of this work was to develop an ELISA assay capable of detecting adulteration of goat milk and its products with bovine milk in China. Polyclonal antibodies against bovine β-casein were used and modified by mixing them with lyophilized Saanen goat β-casein (blocking) to improve the specificity of the antibodies. The blocked antibodies recognize some specific epitopes of bovine β-casein with no cross-activity with bovine α-casein, κ-casein and whey protein. The absorbance values of the indirect ELISA showed a linear relationship to the adulteration concentration of bovine milk in the range of 2%-50%, which can be applied to quantify adulteration of bovine milk. There was no significant difference in titration curves between Saanen and Guanzhong goat milk, and the detection limits were all 2% for goat caseins, raw milk and heat-treated milk. Low coefficients of variation (＜10%) of the experiments indicated good repeatability. The ELISA assay is likely suitable for routine detection of cow's milk adulteration of Shaanxi goat's milk.