Effect of NaCl and ripening time on spore germination by measuring the hydrogen production of Clostridium tyrobutyricum UC7086 in a hard cheese model

This study evaluated the effects of NaCl and ripening time on spore germination of Clostridium tyrobutyricum by analysing the related production of hydrogen in a cheese model. The new approach of this work was to develop a hard cheese model Grana Padano and Parmigiano Reggiano, without the brining stage, that was then cut and ripened at three different times (3, 6, 9 months), freeze-dried and reconstituted with the addition of C. tyrobutyricum spores and different salt concentrations, while maintaining for all cheese models a fixed moisture of 36% ± 1%. Interestingly, a concentration of NaCl near to 0.3% reduced hydrogen production, and therefore germination, at 3 months and completely inhibited it at 6 and 9 months. A 0.5% salt concentration no hydrogen production was observed at all ripening times. In contrast at 9 months of maturation no hydrogen production was observed without any effect due to the salt concentration.