Irradiation effect on α- and β-caseins of milk and Queso Blanco cheese determined by capillary electrophoresis

Milk and Queso Blanco cheese were exposed to irradiation with doses of 1, 2, 3, 5, and 10 kGy to investigate the irradiation effect on α- and β-casein using a capillary electrophoresis. αS1-Casein to total protein ratio in raw milk was decreased from 19.63% to 8.64% by 10 kGy of gamma irradiation. The ratio of αS1- to αS0-casein was also decreased from 1.38 to 0.53, which showed αS1-casein is more susceptible to gamma irradiation than αS0-casein. Similarly, αS1-casein to total protein ratio in Queso Blanco cheese was decreased from 17.48% to 7.82% and the ratio of αS1- to αS0-casein was decreased from 1.16 to 0.43 by 10 kGy of gamma irradiation. Dose-dependent reduction of βA1-casein was also found. βA1-Casein to total protein ratios in raw milk and Queso Blanco cheese were decreased from 22.00% to 14.16% and from 21.96% to 13.89% after 10 kGy, respectively. The ratios of βA1- to βA2-casein were from 1.10 to 0.64 and 0.93 to 0.57 in milk and Queso Blanco cheese, respectively. However, αS0-, βB-, and βA3-casein increased by irradiation at 10 kGy. The results suggest that αS1-casein and βA1-casein were more susceptible to gamma irradiation, and may be related to the reduction of milk allergenicity caused by gamma irradiation.