Changes in equilibrium modulus and αs1-casein breakdown during the ripening of port salut argentino cheese as affected by frozen storage

Abstract

The effect of the freezing, frozen storage and thawing on textural parameters and αs1-casein breakdown during the ripening of Port Salut Argentino cheese was studied. Moisture content, salt concentration, casein profiles and asymptotic equilibrium modulus were monitored in control cheeses ripened at 5C and in cheeses, stored at -22C for 30 days, thawed and ripened at 5C, for different ripening times (1, 6, 13, 27 and 56 days) and two sampling zones (central and external). The freezing process significantly increased the rate of αs1-casein and α s1-I-casein hydrolysis. This process may affect the susceptibility of αs1-casein to chymosin attack and also the availability of hydrolytic enzymes released by damaged microorganisms, which may contribute to the faster hydrolysis of αs1-I-casein. The freezing process did not significantly affect the decay rates of asymptotic equilibrium modulus. First order kinetics constants for decay of the asymptotic equilibrium modulus were 3.71 10-2day-1 (control cheeses, central zone), 8.48 10-2 day-1 (control cheeses, external zone), 4.52 10 -2 day-1 (frozen cheeses, central zone), and 11.43 10 -2 day-1 (frozen cheeses, external zone). Significant differences in the decay rates of asymptotic equilibrium modulus were found between central and external zones in control and frozen cheeses primarily due to differences in moisture contents of the sampling zones.