A Quick Novel Method to Detect the Adulteration of Cow Milk in Goat Milk

This study was to demonstrate a rapid novel method for detection of adulterated cow milk in goat milk using modified staining protocol after native polyacrylamide gel electrophoresis (PAGE). Samples of cow milk and goat milk containing 0, 0.5, 1.0 and 2.0% (v/v) of cow milk were analyzed. Low levels of cow milk mixed in goat milk were identified by the presence of higher mobility of $\beta$-lactoglobulin A ($\beta$-Lg A) in cow milk. By mini-gel electrophoresis, a distinguishable protein profile was visualized in 25 min using the modified Coomassie blue staining solution, in which methanol (50%) was replaced with ethanol (20%) and the concentrations of Coomassie blue and acetic acid were reduced from 2 to 0.13% and 10 to 5%, respectively. To visualize the milk proteins, gels in the staining solution were water-bathed in boiling water for 5 min and then cooled down immediately for 3-5 min. The sensitivity of this method is relatively high, allowing examination of 1% cow milk in goat milk. The procedure presented here is also very cost-effective due to less reagents needed. This simplified method would be useful and applicable to dairy industry for routine examination of goat milk.