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

Abstract

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 alpha- and beta-casein using a capillary electrophoresis. alpha(S1)-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 alpha(S1) to alpha(S0)-casein was also decreased from 1.38 to 0.53, which showed alpha(S1)-casein is more susceptible to gamma irradiation than alpha(S0)-casein. Similarly, alpha(S1)-casein to total protein ratio in Queso Blanco cheese was decreased from 17.48% to 7.82% and the ratio of alpha(S1)- to alpha(S0)-casein was decreased from 1.16 to 0.43 by 10 kGy of gamma irradiation. Dose-dependent reduction Of beta(A1)-casein was also found. beta(A1)-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 beta(A1)- to beta(A2)-casein were from 1.10 to 0.64 and 0.93 to 0.57 in milk and Queso Blanco cheese, respectively. However, alpha(S0)-, beta(B)-, and beta(A3)-casein increased by irradiation at 10 kGy. The results suggest that alpha(S1)-casein and beta(A1)-casein were more susceptible to gamma irradiation, and may be related to the reduction of milk allergenicity caused by gamma irradiation. (C) 2008 Elsevier Ltd. All rights reserved.