The effect of irradiation and elevated temperature on the ripening of cheddar cheese

English: Proteolysis and lipolysis are important biochemical events in the ripening of cheese to contribute to the development of flavour and texture. The characteristic proteolysis of each type of cheese is brought about by the enzymes used in the manufacturing process, e. g. rennet, as well as enzymes from the specific microbial cultures used in each cheese type. The microbial and chemical development can be manipulated by external conditions such as ripening temperature and irradiation. In the current study the effect of temperature together with irradiation on the ripening of Cheddar cheese was investigated. Cheddar cheeses were irradiated after 4 days of ripening at 8 °c and 16°C at a dose of 4kGy and ripening continued up to 12 weeks with unirradiated cheeses ripened at 8 °c and 16°C as controls. In asensorical comparative study, the cheeses were evaluated as not being different in taste. There were no significant differences in the free fatty acid content of the cheeses but the irradiated cheeses and cheese ripened at 16°C had higher TBA-values. The WSNfTotal N (water-soluble nitrogen /total nitrogen) of the cheese ripened at 8 °c was significantly different than that of the other cheeses after 2 weeks, but then reached the same levels as the treated cheeses after 6-12 weeks. The Urea-polyacrylamide gel electrophoresis of the WISF indicated that the cheese ripened at high temperature matures faster than the cheese ripened at low temperature for both the unirradiated and the irradiated cheeses, whereas the irradiated cheeses showed different peptide development over the same period of ripening. The RP-HPLC of the cheeses indicated a difference in peptide profiles of the unirradiated and irradiated cheese ripened at 16°C, and the irradiated cheese ripened at 8 °c from the unirradiated cheese ripened at 8°C.