A study to compare procedures and interventions for removing physical and bacterial contamination from beef carcasses was conducted in six carcass conversion operations that were representative of modern, high-volume plants and located in five different states. Treatment procedures included trimming, washing, and the current industry practice of trimming followed by washing. In addition, hot (74 to 87.8°C at the pipe) water washing and rinsing with ozone (0.3 to 2.3 ppm) or hydrogen peroxide (5%) were applied as intervention treatments. Beef carcasses were deliberately contaminated with bovine fecal material at >4.0 log colony-forming units (CFU)/cm2 in order to be better able to observe the decontaminating effects of the treatments. Carcasses were visually scored by 2 to 3 trained personnel for the level of gross contamination before and after treatment. Samples (10 by 15 cm, 0.3 to 0.5 cm thick) for microbiological testing were excised as controls or after application of each procedure or intervention and analyzed for aerobic mesophilic plate counts, Escherichia coli Biotype I counts, and presence or absence of Listeria spp., Salmonella spp., and Escherichia coli O157:H7. Average reductions in aerobic plate counts were 1.85 and 2.00 log CFU/cm2 for the treatments of trimming-washing and hot-water washing, respectively. Hydrogen peroxide and ozone reduced aerobic plate counts by 1.14 and 1.30 log CFU/cm2, respectively. In general, trimming and washing of beef carcasses consistently resulted in low bacterial populations and scores for visible contamination. However, the data also indicated that hot- (74 to 87.8°C at the pipe) water washing was an effective intervention that reduced bacterial and fecal contamination in a consistent manner.
Color and oxidative rancidity were determined for chilled (3 ע 2ЊC) and frozen (Ϫ17 ע 3ЊC) boneless pork chops packaged in vacuum or air and irradiated to an absorbed dose of 0, 1.5 or 2.5 kGy (chilled) or 0, 2.5 or 3.85 kGy (frozen) of electron beam or cobalt 60 irradiation. Irradiation of vacuum-packaged chops produced redder, more stable (color and rancidity) product. More pronounced oxidative rancidity and less stable display color were noted for samples irradiated in aerobic packaging. Irradiation source had varying but limited effects on color and rancidity. Optimum packaging conditions can control color and rancidity changes in boneless chops, thereby enabling irradiation to be a useful intervention technology.
stock culture was subcultured monthly on a tryptic soy agar (TSA, DIFCO, Detroit, MI) slant at 4ЊC. Working cultures were transferred from the stock culture by inoculating brain heart infusion (BHI, DIF-CO, Detroit, MI) broth. The culture was incubated at 37ЊC for 20h to obtain 10 9 colony forming units (CFU)/mL. After incubation, cells were harvested by centrifuging the culture at 5,500 ϫ g for 10 min at 4ЊC, using a JA-14 rotor (Beckman J2-HS centrifuge, Beckman Instruments, Inc., Palo Alto, CA). The cell pellet was resuspended to original volume in 0.1% peptone (DIFCO, Detroit, MI), and used to inoculate beef trimmings. The suspension was plated on MacConkey sorbitol agar (MSA, DIFCO, Detroit, MI) containing Rifampicin (100 ppm; Sigma Chemical Co., St. Louis, MO) using a Spiral Plater TM (Model 500 D, Spiral Biotech Inc., Bethesda, MD) to provide an estimate of inoculum size. Sample preparation for antimicrobial testsFresh beef trimmings ( 85% lean and 15% adipose; 4 days postmortem) were obtained from the Meat Lab of the Department of Animal Sciences and Industry, KSU. One treatment and two controls were used. E. coli O157:H7 was added to the beef trimmings to provide 10 7 CFU/g, and mixed for 4 min using a Hobart mixer (Hobart Corp., Troy, OH). LS and sterile water, treatment and control, respectively, were added to the inoculated trimmings for a final concentration of 8%, and mixed for 4 min. A second control, without LS, water or E. coli O157:H7, was mixed for 4 min and used for psychrotrophic counts. The treated sample and controls were coarsely ground (1.27 cm), followed by a fine grind (0.32 cm) using a sterile grinder (Hobart Corp., Troy, OH). Patties were made (70-90g), using a manual patty maker (Holly JR., Hollymatic Corp., Chicago, IL), packaged (Harbro Packaging Company, Chicago IL) aerobically, heat sealed (Multivac A300(16), Germany), and stored in the dark at 4ЊC for up to 3 days. The treated sample and both controls were obtained from the same batch of trimmings. Three replicates were performed for each treatment and control. Microbial analysisImmediately after inoculation, duplicate surface samples (25g) were taken each from inoculated, treated (LS or water), and noninoculated beef trimmings to check initial E. coli O157:H7 populations, antibacterial effects of treated trimmings, and psychrotrophic counts, respectively. Surface samples ( 0.7 cm deep) were taken from the prepared trimmings with a sterile scalpel and tongs. Duplicate samples (25g) also were taken from the LS treated, inoculated controls, and non-inoculated control patties at day 0, 1, 2 and 3. Samples were placed in a filtered stomacher bag (Seward, London, UK), 225 mL of 0.1% peptone water was added, and stomached for 2 min (Model 400, Tekmar, Inc., Cincinnati, OH). Serial dilutions were prepared in peptone water (0.1%) and spiral plated on MSA containing 100 ppm Rifampicin for the inoculated samples, and on plate count agar (PCA, DIFCO, Detroit, MI) for the non-inoculated controls. The plates for inoculated samples were incub...
Escherichia coli O157:H7 emerged as a foodborne pathogen in 1982 and can cause three major disease syndromes (hemorrhagic colitis, hemolytic uremic syndrome, and thrombotic thrombocytopenic purpura). Outbreaks caused by E. coli O157:H7 have been linked to ground beef, milk, apple cider, lettuce, radish and alfalfa sprouts, and water. In 1994, an outbreak of E. coli O157:H7 infection was linked to dry, fermented, pork and beef salami. In response to this first implication of a dry fermented sausage product, the United States Department of Agriculture/Food Safety Inspection Service developed guidelines requiring sausage manufacturers to validate that their processes achieve a five‐log reduction of E. coli O157:H7. Various validation studies have shown that E. coli O157:H7 is able to survive in sausages that are fermented and then dried to various moisture‐to‐protein ratios of 2.3, 1.9, or 1.6:1. Additional thermal processing methods or longer fermentation processes were utilized to achieve 5‐log reductions.
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