Western blotting of native and denatured bovine beta-lactoglobulin to detect addition of bovine milk in cheese

Western blotting of bovine beta-LG is a valid method to detect adulteration by pasteurized bovine milk, by UHT bovine milk, or by heat-denatured bovine whey proteins in cheeses made of milk from other species. Use of PAGE of whey or isoelectric focusing of beta-LG isolated from the casein fraction was followed by immunodetection with anti-bovine beta-LG antiserum. The selectivity of the antisera to react with native and denatured beta-LG was studied. Detection limits of native and denatured beta-LG standard solutions were 10 and 50 pg/mu l, respectively. Immunoblotting of the native-PAGE plates of whey proteins from cheese allows detection of bovine heat-denatured whey proteins or pasteurized bovine milk added to cheese even at <1%. At <1% adulteration by UHT milk immunoblotting of the isoelectric focusing plates of beta-LG isolated from casein micelles is a better detection method. Adulteration with bovine milk or denatured whey proteins in percentages >1% can be detected by either Western blotting methods.