Proteolysis, texture and colour of a raw goat milk cheese throughout the maturation

摘要

Changes on chemical and textural parameters were studied throughout maturation of PDO Ibores cheese. NCN/TN (non-casein nitrogen/total nitrogen) values were significantly modified (P 0.001) throughout maturation, and significantly, lower values were observed at day 1 than at day 30, 60 and 90. Non-protein nitrogen/total nitrogen (NPN/TN) was not significantly changed during the ripening process (P 0.05). Therefore, proteolysis extent (casein degradation and ‘ripening depth’) took place at initial stage and was limited throughout Ibores cheese maturation. In addition, since casein nitrogen decreased during the first month of ripening without a simultaneous increase in NPN/TN, this likely indicates that the large fragments of caseins liberated during this period are not further degraded into smaller products. Primary proteolysis (resulting from the action of endoproteases on caseins) is thus far more important than secondary proteolysis during this period. Moreover, secondary proteolysis remains limited along the 90 days. Polypeptide nitrogen significantly increased at day 30 from casein degradation compared to day 1, while free amino acids (FAA) content significantly increased during maturation process. In addition, hardness and adhesiveness values significantly increased, but cohesiveness and springiness significantly decreased up to day 60. Variables such as dry matter, NCN/TN and polypeptide nitrogen showed high correlations with textural parameters. Principal component analysis (PCA) of variables divided the Ibores cheeses according to their ripening: early, middle or late ripening.