Profiling of caseins in cows', goats' and ewes' milk and dairy products by reversed-phase high-performance liquid chromatography

The aim of this study was to evaluate the composition of caseins in milk and dairy products employing a fast and effective method of reversed-phase high-performance liquid chromatography (RP-HPLC). An additional task was to separate and identify alpha(S1)- and alpha(S2)-caseins by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) and thus confirm their presence in the analysed samples. A total of 120 milk samples (cows', goats' and ewes') and 46 samples of dairy products (cheese, yoghurt) obtained from farms and milk bars in Czech Republic were analysed by RP-HPLC. All main casein components (alpha(S1)-, alpha(S2)-, beta- and kappa-casein) were identified and quantified. Statistically significant differences between individual caseins in various samples of milk and dairy products were detected. RP-HPLC profiling of samples showed that the presence of individual caseins depends primarily on the animal source of milk but also on the technological treatment of dairy products. The quantity of alpha(S1)-casein, which has the most pronounced allergenic potential, varied significantly between different samples. The current study demonstrated good performance of the novel approach for RP-HPLC analysis of alpha(S1)- and alpha(S2)-caseins utilizing in-house prepared analytical standards as well as provided valuable data regarding the casein profile of milk and dairy products on the market.