Evaluation of proteolytic activity of Staphylococci in Soppressata Molisana, a typical Southern Italy fermented sausage.

Two Staphylococcus xylosus strains were separately used as starter cultures in Soppressata Molisana, a typical Southern Italy fermented sausage, with the aim to obtain an overviewof the roleof microbial proteolysis. Microbial counts, pH trendsand soluble N (NPN, peptideand total amino acid content) were monitored throughout the ripening (26 days)and at the endof storage (94 days) in pork fat or under vacuum packaging. A lower productionof soluble N was observed in the traditional batchand in products inoculated with non-proteolytic Staphylococcus xylosus strain. Moreover, staphylococci growth was less vigorous than that observed in the sample inoculated with the proteolytic strain. The results show that the proteolytic phenomena, ascribable to bacterial activity, can take on a meaningful role when the food matrix has been colonised by strains having powerful proteolytic capacities. In fact, the increasing trend in NPN/NT, small peptidesand total free amino acids, shown in batch inoculated with proteolytic Staphylococcus xylosus can be justified by a considerable proteolyticand peptidasic capacity exhibited by the strain added as starter. This work could contribute to define the microbiological roleof proteolysis occurring in fermented sausage.