Biochemical Characterization of Non-commercial <i>Penicillium</i> Strains as Mould-ripened Cheese Starters

<p>　Aiming to characterize as mould-ripened cheese starters, proteolytic and lipolytic activities were evaluated towards non-commercial Penicillium roqueforti strains K10, R26, and Penicillium caseicolum strain DL102 in this study. Further, time course of pH, volatile aroma compounds, amino acid composition, peptide profiles, and production of mycotoxins typically found in food stuffs were monitored by using a curd slurry medium in which those strains were inoculated independently. Consequently, K10 and R26 showed lower maximum pH values compared to a commercial P. roqueforti strain CB2 used as control, meanwhile DL102 showed slower time-dependent pH change compared to Penicillium camemberti strain PCTT033, reflecting their significantly lower proteolytic activities in the curd slurry medium. K10 and R26 gave 33% and 39%, respectively, of total free amino acids in the curd slurry medium compared to CB2, whereas DL102 produced 99% of total free amino acids compared PCTT033. Lipolytic activities of the three non-commercial strains were likely to be lower than the commercial strains. Profiles of volatile aroma compounds were the same among K10, R26, and CB2, whereas DL102 showed less variation than PCTT033. Production of several potential bioactive peptides were confirmed in the curd slurry medium inoculated with the non-commercial strains. Mycotoxin production was undetectable for all the non-commercial strains, suggesting their safety assurance. To conclude, the non-commercial strains K10, R26, and DL102 were highly potential as starters for commercial production of mould-ripened cheeses, although further studies are required to elucidate practical aspects of their industrial applications.</p>