Lysozyme (LZ) is used in several cheese varieties to prevent late blowing which results from fermentation
of lactate by Clostridium tyrobutyricum. Side effects of LZ on lactic acid bacteria population and free amino
acid pattern were studied in 16 raw-milk hard cheeses produced in eight parallel cheese makings
conducted at four different dairies using the same milk with (LZþ) or without (LZ-) addition of LZ. The
LZ-cheeses were characterized by higher numbers of cultivable microbial population and lower amount
of DNA arising from lysed bacterial cells with respect to LZ cheeses. At both 9 and 16 months of
ripening,Lactobacillus delbrueckiiandLactobacillus fermentumproved to be the species mostly affected by
LZ. The total content of free amino acids indicated the proteolysis extent to be characteristic of the dairy,
regardless to the presence of LZ. In contrast, the relative patterns showed the microbial degradation of
arginine to be promoted in LZþcheeses. The data demonstrated that the arginine-deiminase pathway
was only partially adopted since citrulline represented the main product and only trace levels of ornithine were found. Differences in arginine degradation were considered for starter and non-starter lactic
acid bacteria, at different cheese ripening stage