Proteolysis during ripening of soft cheese. II-effect of milk-clotting enzyme on cremoso argentino cheese ripening

摘要

Proteolysis is a major event during cheese ripening. Milk-clotting enzyme play an important role in the proteolysis process. The objective of the present work was to investigate the ripening of Cremoso Argentino cheese, a soft variety with high moisture content. Two types of cheese were manufactured: control and experimental rennet-free cheese. Proteolysis was markedly higher in control cheese than in rennet-free cheese. The nitrogen content of soluble fractions at pH 4.6 and in 2% trichloracetic acid for control cheese at the end of ripening (21 days) was twice as high as that of experimental cheese. The soluble nitrogen in 12% trichloracetic acid was also significantly higher for control cheese. On the other hand, the amount of soluble nitrogen in phosphotungstic acid (amino acids and oligopeptides) was very similar for both types of cheeese. Urea-PAGE electrophoretic patterns showed an extensive degradation of #alpha#_(sl)-casein in control cheese giving the #alpha#_(sl)-l fraction. A such hydrolysis was not detected in experimental cheese. RP-HPLC chromatograms of soluble and insoluble fractions at pH 4.6 showed that rennet-free cheese did not undergo the hydrolysis #alpha#_(s1)-casein as control cheese, #beta#-casein remained intact in both cases. Analysis of free amino acid did not evidence any significant difference between control and rennet-free cheeses, the total amount of free amino acids being very low in both cases.