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This study evaluated a prototype steam pasteurization system (SPS) for the decontamination of beef trimmings. The three stated objectives to the project were as follows. 1) To determine the effects of steam pasteurization on descriptive sensory attributes. 2) To determine a recommended integrated steam pasteurization process which could be applied in a commercial ground beef production facility. 3) To continue process development and anti-microbial validation for SPS systems for surface decontamination of beef trimmings destined for ground meat products.
Both lean and fat beef trimmings were inoculated with pathogenic microorganisms and then treated with steam for various periods of time. The effect of over-pressurized steam on Escherichia coli O157:H7, Salmonella typhimurium, and Listeria innocua was evaluated at four temperatures (180°, 190°, 200°, and 210°F) and six treatment times (0, 3, 6, 9, 12 and 15 sec.). The tissue was inoculated with each pathogen before steam pasteurization. Microbial analysis was performed before and after treatment. In order to bring the surface temperature back to pre-treatment levels after pasteurization, the meat was washed with cold water.
Results showed a visible color change to the beef trimmings that was evident both before and after grinding. Because of the substantial changes in beef color resulting from this technology, the pasteurized trimmings would not be marketable as retail ground beef but could have an application for foodservice ground beef or frozen beef patties. Findings that relate to Objective 2 showed a significant reduction in pathogen levels for specific time and temperature combinations. The lowest time/temperature combination that significantly reduced all pathogens was 200°F for 6 seconds. The combination that was most effective for reducing pathogen levels was the 210°F for 15 second treatment. As found in Objective 1 though, the color of the meat changed drastically with higher temperatures and longer treatment times, reducing the desirability of the end product. As for Objective 3, the highest reduction in microbial populations on lean trimmings were obtained at 15, 20, and 25 seconds of steam treatment, with mean reductions ranging from 1.10 to 1.69 log10 per gram. For fat trimmings, the highest reductions were obtained after 30 seconds of steam pasteurization, with mean reductions ranging from 1.5 to 2.22 log10 per gram.