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United States Department of Agriculture

Agricultural Research Service

Title: Effects of Steam-Vacuuming and Hot Water Spray Wash on the Microflora of Refrigerated Beef Carcass Surface Tissue Inoculated with Escherichia Coli O157:h7, Listeria Innocua, and Clostridium Sporogenes

item Dorsa, Warren
item Cutter, Catherine
item Siragusa, Gregory

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 10, 1996
Publication Date: N/A

Interpretive Summary: The beef processing industry would like to use effective methods to eliminate pathogenic bacteria from beef carcasses. We have previously shown that washing carcasses with hot water and/or removing extraneous matter with a steam-vacuum sanitizer are effective means of reducing overall bacteria from beef carcasses. Since beef is not consumed immediately after the application of these carcass decontamination methods, this experiment was designed to test their long range effectiveness. Fresh cattle feces spiked with 300,000 bacteria (E. coli O157:H7, Listeria innocua, Clostridium sporogenes) per square centimeter of meat and containing spoilage and other naturally occurring bacteria, were used to contaminate the meat prior to all treatment methods. The effect of the treatments on the meat was tracked over time by monitoring the levels of E. coli O157:H7, L. innocua, and C. sporogenes, along with total bacteria, and spoilage bacteria at selected times during refrigerated storage for 21 days. All treatments initially reduced total bacteria, spoilage bacteria, E. coli O157:H7, L. innocua, and C. sporogenes by 99.9%. E. coli O157:H7 did not grow to the original contamination levels of about 300,000 bacteria per square centimeter of meat for the duration of the refrigerated storage period, and C. sporogenes numbers continued to decline for the duration of the 21 days. These results demonstrate that the beef processing industry can use any of these methods to effectively reduce the number of certain pathogenic and spoilage bacteria from beef carcasses during processing and subsequent refrigerated storage.

Technical Abstract: The fate of several bacterial populations on beef carcass surfaces was examined immediately following hot water washes (W) delivered through a beef carcass wash cabinet or application of steam-vacuum (SV) as well as storage up to 21 d at 5 deg C under vacuum-packaged conditions. Fresh, unaltered bovine feces spiked with antibiotic resistant strains of Escherichia coli O157:H7, Listeria innocua, and Clostridium sporogenes were used to inoculate beef carcass tissue prior to W or SV treatment. The effect of treatments on inoculated tissue was tracked by monitoring levels of the marked bacteria along with mesophilic aerobic bacteria, lactic acid bacteria, and pseudomonads for up to 21 d at 5 deg C storage. Initial bacterial populations following any of the treatments were not statistically different (P>.05) from one another; however the combination of SV followed by W consistently produced arithmetically greater bacterial reductions. In general, all treatments produced initial reductions of up to 2.7 log10 CFU/cm**2 for APC, lactic acid bacteria, and L. innocua, but by 14 d bacterial numbers had increased to levels of >/= 7 log10 CFU/cm**2. E. coli O157:H7 was initially reduced by as much as 3.4 log10 CFU/cm**2 and did not grow to original inoculation levels for the duration of the experiment. Vegetative counts of C. sporogenes were initially reduced by as much as 3.4 log10 CFU/cm**2 and numbers continued to decline for the duration of the study. These results indicate that the use of W and SV independently and in combination effectively reduces general and specific bacterial populations from beef carcass tissue immediately after treatment.

Last Modified: 5/5/2015
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