A CROSS-LINKING APPROACH FOR STUDYING MUTUAL SPATIAL RELATIONSHIPS OFPROTEIN-COMPONENTS IN CHEESE

A cross-linking approach was developed to investigate the distribution of casein components in milk and in commercial cheeses. Cross-linking was carried out with glutaraldehyde, followed by electrophoretic sepa ration of reaction products obtained after different times of exposure to glutaraldehyde. in raw milk alpha(s)-casein and beta-casein showed nearly identical reactivity with glutaraldehyde, while whey proteins did not react. Thus, the method appeared suited to reveal spatial prox imity of the reacting proteins. On these bases, the cross-linking proc edure was applied to homogenates of 4 commercial cheeses, differing in ripening time, thermal treatment and texture (Mozzarella, Caciotta, T aleggio, and Processed cheese). Kinetics of cross-linking of individua l casein components allowed to differentiate among thermally processed and unprocessed ones, with the former giving a reactivity to glutaral dehyde dose to that observed with raw milk. Major differences were fou nd between Taleggio and Caciotta, in which beta-casein and para-kappa- casein seemed the most sensitive indicators of changes in micellar str ucture associated with cheese ripening.