Milk species identification in cheese varieties using electrophoretic, chromatographic and PCR techniques

Different methods were applied to standard mixtures of milk from different species and to model cheeses of different ages to study their applicability for the detection of cows' milk and determination of the percentage of cows' milk in mixed milk cheeses. Urea-polyacrylamide gel electrophoresis (urea-PAGE) and anion-exchange high performance liquid chromatography (HPLC) of caseins was restricted to the control of the adulteration of milk. Isoelectric focusing (IEF) of γ-caseins according the EU reference method was well suited for detection of cows' milk even in matured cheese, but could not discriminate ewes' milk from goats' milk. IEF and cation-exchange HPLC of para-κ-caseins were appropriate for differentiation of bovine, ovine and caprine milk. Urea-PAGE and IEF of whey proteins was useful for the species authentication of whey cheeses. Polymerase chain reaction using species-specific primers was a highly sensitive technique for the qualitative detection of cows' milk even in overripe mixed cheese.