88D-20 |
Surface bacterial penetration as a result of hydrodynamic shockwave treatment of beef steaks |
T. A. LORCA1, M. D. Pierson1, and J. R. Claus2. (1) Dept. of Food Science & Technology, Virginia Polytechnic Institute & State Univ., FST Bldg., Lab 20, Blacksburg, VA 24061-0418, (2) Meat Science & Muscle Biology Lab., Univ. of Wisconsin, Madison, 1805 Linden Dr. W., Madison, WI 53706 Hydrodynamic shockwave (HSW) treatment destroys portions of muscle fibers via penetration of a large force from the outer surface into the muscle and may thus produce a product which would fall under FSIS sampling and testing programs for non-intact cuts of beef. If the process permits the migration of surface bacteria deep into the muscle, normal cooking may not kill pathogens now protected within the tissue, creating a microbial safety hazard in HSW-treated beef. Marker bacteria were used to determine if HSW treatment of intact beef steaks induced migration of bacteria from the outer surface into the muscle and whether the migration occurred to an extent that the treated steak could pose a microbial safety hazard to consumers. The top surface of raw eye of round steaks was inoculated with either Green Fluorescent Protein (GFP) labeled Escherichia coli (E. coli-GFP) or rifampicin-resistant E. coli (E. coli-rif), individually vacuum packaged, and transported on ice to the Buena Vista Hydrodyne prototype for HSW treatment. HSW treated samples and non-treated controls were transported on dry ice to VA Tech for sampling and examination. Core samples were aseptically removed from the frozen steaks, sectioned with a Cryostat, then examined for viability of E. coli-rif via plating onto microbiological media. Depth of penetration of E. coli-GFP was determined by Laser Scanning Confocal Microscopy. HSW treatment induced limited migration of the marker bacteria into the interior of the steak. For HSW treated samples, cell penetration occurred to a maximum depth of 250 µm from the outer surface. HSW treatment only increased the depth at which marker organisms were found by 150 µm beyond the untreated control. Although HSW-induced bacterial penetration was observed in treated steaks, the extent of penetration does not appear to pose a safety hazard to consumers if cookery precedes consumption.
Session 88D, Food Microbiology: General
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