29F-18 |
Combination effect of bacteriocin and high pressure processing on inactivation of Listeria monocytogenes strains |
H. J. CHUNG1, A. Tay1, A. E. Yousef1, T. H. Shellhammer2, and G. W. Chism, III1. (1) Dept. of Food Science & Technology, Ohio State Univ., 2015 Fyffe Ct., 110 Parker Food Science Bldg., Columbus, OH 43210-1007, (2) Dept. of Food Science & Technology, Oregon State Univ., 100 Wiegand Hall, Corvallis, OR 97331-6602 Listeria monocytogenes is a pathogen that causes serious foodborne disease at low infective doses. The combination of bacteriocin and high pressure processing (HPP) has been previously suggested for inactivation of foodborne pathogens. A newly discovered bacteriocin from Lactobacillus casei showed inhibitory effect against gram-positive and gram-negative bacteria. Combinations of this bacteriocin and HPP may have synergistic effect against Listeria strains. Moreover, the sublethally injured cells by either high pressure treatment or bacteriocin treatment can be inactivated by the combination treatment. The objectives of this study were to investigate the synergistic effect of a new bacteriocin and HPP on inactivating L. monocytogenes and to apply the combined treatment of HPP and bacteriocin in inoculated food systems. Three L. monocytogenes strains, Scott A, V7, and OSY-8578 (Ohio Department of Agriculture) were examined. Cultures were grown for 18 h in tryptose broth at 37°C. One mL aliquots of cultures in plastic bags were treated with bacteriocin (equivalent to 32 unit of colicin) and high pressure processed (350 MPa) for 1-20 min using an ABB Quintus 6 pressure system. Treated and non-treated samples were enumerated on tryptose agar. The combination treatment was carried out in 4 independent and 2 dependent replications. The combination treatment showed synergistic effect on inactivation of Listeria. The combination of bacteriocin and HPP at 350 MPa for 1 min caused more than 4 log reduction in all strains of L. monocytogenes, while each treatment alone caused less than one log reduction. When applied to a meat product (Vienna sausage), the combination of bacteriocin and HPP at 500 MPa for 1 min caused maximum 5 log reduction of L. monocytogenes Scott A. This research indicates the synergistic effect of the treatments against pathogenic L. monocytogenes. This suggests a potential application of the combination treatment of bacteriocin and HPP in foods.
Session 29F, Food Microbiology: Control of foodborne microorganisms by antimicrobials
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