Bacteriocins, mild heat and high pressure for preserving low acid meat products
B. RAY, Dept. of Animal Science, Univ. of Wyoming, PO Box 3354, Laramie, WY 82071-3354
The destabilization of structural and functional properties of membrane is associated with the bacterial cell death caused by high hydrostatic pressure, heat or bioactive peptides, such as bacteriocins of food grade lactic acid bacteria. Although their modes of bactericidal action are different, since they all destabilize the membrane, these parameters could be combined to achieve a higher level of bacterial death.
Using this concept, a 6 to 7 log cycle reduction of foodborne pathogenic and spoilage bacterial cells in bacteriological media was obtained by the combination treatment of 345 MPa for 5 min at 50°C and in the presence of a biopreservative (BP), prepared with pediocin AcH and Nisin A. Comparable viability loss for the pathogenic and spoilage bacteria by the combination treatment was also obtained in product inoculation studies with roast beef, Cotto salami and summer sausage. In storage studies with inoculated levels of pathogenic and spoilage bacteria at 3 to 4 log bacteria/g the combination treatment completely killed the cells as evidenced by no growth being observed during storage of the treated products up to 84 d at 25°C.
In the course of the studies, it was also observed that differences in pressure sensitivity at 25°C among bacterial strains could be eliminated by pressurizing the cells at 50°C. Pressure resistant Listeria monocytogenes strains, associated with foodborne outbreaks, could be completely eliminated from inoculated product packages by the combination treatment of 345 MPa for 5 min at 50° C in the presence of BP; in the absence of BP they were not completely eliminated.
The health hazard associated with the pathogens in ready-to-eat meat products could be controlled by pressurizing the packaged products made with BP and pressurizing at moderate temperature.
Session 6, Effect of combinations of thermal and nonthermal treatments on microbial survival