GAMMA-CASEIN AS A MARKER OF RIPENING AND/OR QUALITY OF GRANA PADANO CHEESE

摘要

Several biochemical reactions occur in cheese during ripening. Among these, proteolysis of beta-casein to produce gamma fractions is one of the most evident. In search of new quality markers, an isoelectric focusing technique in a suitable pH range has been used to evaluate gamma-casein profiles in Grana Padano cheese samples at different times of ripening (from 4 to 36 months). The following ratios between densitometric values were considered: gamma(2)-casein/gamma(1)-casein, gamma(3)-casein/gamma(1)-casein, and gamma(3)-casein/gamma(2)-casein. Another parameter investigated was the presence of modified gamma(2)-casein (with pI = 6.7), which derives from the interaction between gamma(2)-casein and aldehydes coming from microbial metabolism. The appearance of this protein band correlates well with the cheese ripening period. Data shown in this paper indicate that gamma fractions could be considered as new markers of ripening and quality and contribute to the certification of Grana Padano cheese on the international market.