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Browsing by Author "Pruett, Wayne P."

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    Microbial properties of color-modified turkey
    Pruett, Wayne P. (Virginia Tech, 1989-06-04)
    Studies were performed to determine the effect of color modification procedures on the microbial characteristics of turkey thigh meat. Turkey thighs were flaked and then color modified successively with three sodium phosphate buffers (pH 5.8, 7.4, and 8.0). At selected time intervals, flaked unwashed turkey (FUT; control) and color-modified turkey (CMT) stored at 3°C were analyzed for aerobic, psychrotrophic, and coliform bacterial counts. Aerobic and psychrotrophic numbers also were estimated in raw tissues held at -20°C. Cooked FUT and CMT were inoculated with two strain composites of either Salmonella or Listeria monocytogenes and held at 4 and 20OC. Salmonella enteritidis, Salmonella typhimurium, Q. monocytogenes Scott A, and a Q. monocytogenes meat isolate were organisms used in the inoculation studies. Aerobic and psychrotrophic counts were not different (p >0.05) at any sampling interval when numbers in raw EUT were compared to those in raw CMT. Coliform counts in raw FUT did not differ from those in raw CMT (p >0.05) after l day at 3°C. In inoculation studies, numbers of either pathogen generally did not differ (p >0.05) I between cooked FUT and CMT at selected sampling intervals. Salmonella counts declined gradually in cooked samples held at 4°C. By day 3, Salmonella levels increased more than 6 logs in tissues held at 20°C. L. monocytogenes counts increased approximately 5 logs in cooked FUT and CMT held at 4°C for 14 days. Numbers increased more than 5 logs in samples stored at 20°C for 48 hr. Although a significant (p <0.05) factor in some studies, color modification was not considered to have a major effect on microbial growth in altered thigh.
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    Sanitizer efficacy against bacteria attached to synthetic meat processing surfaces
    Pruett, Wayne P. (Virginia Tech, 1993)
    The effectiveness of selected sanitizers against bacteria attached to synthetic meat processing surfaces was determined. In initial experiments, in vitro suspensions of Shw. putrefaciens, P. fragi, S. typhimurium, and L. monocytogenes were challenged with sanitizers according to the AOAC Germicidal and Detergent Sanitizer Test (GDST). Germicides employed were chlorine (200 ppm), iodophor (25 ppm), quaternary ammonium compound and phosphoric acid (200 ppm), and peracetic acid (185 ppm). In subsequent studies, the same sanitizers were tested against bacteria attached to polyvinyl chloride, polyurethane, and high density polyethylene surfaces. Test surfaces in sterile poultry slurries were inoculated with bacterial cultures, agitated (100 rpm) for 2 hr at 18°C, and then incubated for 22-28 hr at 26°C (Shw. putrefaciens and P. fragi) or 37°C (S. typhimurium and L. monocytogenes). Scanning electron microscopy (SEM) was employed to determine microbial-surface interactions. Attached organisms remaining on surfaces after vortexing were challenged with germicides. In some cases, surfaces were treated with detergents before applying Sanitizers. Impedance microbiology was used to estimate surviving bacterial populations remaining after chemical treatments. All test sanitizers reduced levels of suspended bacterial cultures >5 logs after 30 sec, and thus, were deemed acceptable according to GDST guidelines. From SEM micrographs, the 22-28 hr surface biofilms of Shw. putrefaciens, S. typhimurium, and L. monocytogenes could be characterized as single adherent cells or cell monolayers. Conversely, the P. fragi biofilm occurred as cell aggregates or microcolonies. Although sanitizers were effective according to GDST results, in many instances, attachment to surfaces increased bacterial resistance to germicidal agents (a 5 log reduction was not observed even after 1 min of chemical exposure). Peracetic acid, overall, was the most effective sanitizer in reducing levels of attached bacteria. Where resistance to other germicides could be observed for up to 20 min, peracetic acid typically eliminated biofilm populations after 1 min. Treatment of surfaces with detergents and then sanitizers led to more effective reductions of attached bacteria. The extensive fibril production by attached S. typhimurium (versus other attached organisms in this research) may explain the greater overall sanitizer resistance of this organism as compared to other test bacteria. However, higher initial numbers of surface bacteria (time 0) may have been the reason for greater sanitizer resistance (higher survivor levels) in some experiments. It is hoped that results of this study can aid processors in developing sanitizer schemes to minimize processing surface contamination with organisms of quality and safety concern.