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Inactivation of Staphylococcus aureus and Listeria monocytogenes in milk and cream of chicken soup by high hydrostatic pressure and bacteriocins

Alpas, Hami
By the application of HHP; 5.50 and 5.70 log cycle reduction was obtained for S. aureus 485, in milk and cream of chicken soup samples, respectively. Storage of HHP treated milk samples for 24 h at 4degreesC gave positive result for S. aureus 765 where no growth was observed for L. monocytogenes strains. Incubation of food samples for an additional 48 h at 37degreesC showed growth of L. monocytogenes strains as S. aureus strains. When a bacteriocin-based biopreservative (BP1) was combined with pressurization more than 8 log-cycle reduction in cell population of the resistant strains of S. aureus and L. monocytogenes was achieved in milk. Milk and cream of chicken soup samples were stored at 25degreesC and milk samples showed no growth up to 30 day where as Gram-positive bacterial strains in cream of chicken showed growth after 3 days with a rapid increase in cell number thereafter.