Biogenic amines producing and degrading bacteria: A snapshot from raw ewes' cheese

Tyramine and histamine are considered the most toxic biogenic amines (BAs) and are often found in high concentrations in fermented foods, such as cheese, and beverages. Their control is critical to assure food safety. Recently the use of food borne BAs degrading bacteria has been proposed. The aim of this study was to isolate bacteria from Incanestrato di Castel del Monte, a raw ewe's cheese, unable to produce histamine and tyramine and, at the same time, able to degrade them. Twenty-four strains with different BAs-producing and degrading abilities were isolated. Twelve strains produced tyramine, while none of them histamine in agreement with molecular data which showed the absence in these strains of hdc gene. Only 2 strains did not degrade tyramine, while the others showed a degradation % ranging from 3.83 +/- 0.15 to 62.45 +/- 3.98. Tyramine degradation % varied from 6.23 +/- 012 to 70.74 +/- 2.15. The most interesting strains appeared to be A422 (L. casei), and A143 (E. casseliflavus), since they show a quite high % of degradation of both BAs, and did not show decarboxylase activity. Selected bacteria could be used as starter culture to reduce tyramine and histamine concentration in raw milk cheeses.