Determination of whey proteins in different types of milk

Protein analysis is very important both in terms of milk protein allergy, and of milk and dairy product adulteration (P-lactoglobulin may be an important marker in the detection of milk adulteration). The aim of this study was to detect major whey proteins alpha-lactalbumin and beta-lactoglobulin and their genetic variants by reversed-phase high-performance liquid chromatography. Milk samples from cows (n = 40), goats (n = 40) and sheep (n = 40) were collected at two farms and milk bars in the Czech Republic from April to June 2010. The concentration of alpha-lactalbumin was higher in goat's milk (1.27 +/- 0.05 g.l(-1), P < 0.001) and cow's milk (1.16 +/- 0.02 g.l(-1), P = 0.0037) compared to sheep's milk (0.95 +/- 0.06 g.l(-1)); however, concentration of alpha-lactalbumin in goat's milk and cow's milk did not differ significantly (P < 0.05). Goat's milk contained less beta-lactoglobulin (3.07 +/- 0.08 g.l(-1)) compared to cow's milk (4.10 +/- 0.04 g.l(-1), P < 0.001) or sheep's milk (5.97 +/- 0.24 g.l(-1), P < 0.001). A highly significant positive correlation (r = 0.8686; P < 0.001) was found between fraction A and B of beta-lactoglobulin in sheep's milk, whereas in cow's milk there was a negative correlation (r = -0.3010; P = 0.0296). This study summarizes actual information of the whey protein content in different types of milk which may be relevant in assessing their allergenic potential.