ABSTRACT
Beef strip loins were sprayed with 1.5% (vol/vol) lactic acid before and/or after 14, 28, 56, 84, and 126 days of vacuum-packaged storage at -1.1 or 2°C to assess the effects on bacteria. Five different treatment combinations including a control (no spray treatment) and one treatment with prestorage acid spray followed by poststorage water spray (A/W) were evaluated. Compared to the controls, 97% of all acid-treated loins had lower microbial counts throughout the storage period. Prestorage acid spray (A/0) was more effective than poststorage acid spray (0/A)with the greatest effects (P < 0.05) being observed on day 28, where the bacterial population was reduced by 1.9 and 1.5 log CFU/cm2 for loins stored at -1.1 and 2°C, respectively. Microbial counts for loins with A/A(acid spray both before and after vacuum storage) or A/W treatments were lower than but not significantly different from A/0 (P > 0.05). Poststorage washing resulted in a minimal decontaminating effect, irrespective of the washing agent used. In addition, single spray treatment immediately after fabrication seems more effective and practical than a double spray. Temperature main effects showed that colder temperature (-1.1 versus 2°C) reduced (P < 0.03) microbial growth throughout the storage period. Salmonella contamination was not detected in any samples; however, 28% of the control and 4% of the spray-treated loins were positive for Listeria spp. Appropriate time of acid application in combination with colder storage temperature improved the microbiological quality of meat for at least four weeks.
ABSTRACT
Beef carcass sides (n = 48) were selected randomly on three different days in a commercial processing facility and microbiologically analyzed before being moved to the cooler. Four types of samples were obtained per side from the inside round area: no trim and no wash (NTNW); trim, but no wash (TNW); trim and wash (TW), and no trim but wash (NTW). A flame-sterilized knife, forceps, and scalpel were used for each trimming treatment and sampling. Significant differences (P < 0.05) were observed in mean aerobic plate counts (APCs) between treatments. The greatest reduction in APC (log10 colony forming units [CFU] per cm2) was observed in TNW samples followed by TW and NTW, with the corresponding mean APC reductions relative to NTNW being 3.0, 0.9, and 0.3, respectively, indicating that trimming can be an effective control point in reducing bacterial contamination in the slaughter process. Although TNW samples, had the lowest counts, samples from the same location after wash (TW) had counts 2 log cycles higher than TNW samples. These results indicate that washing spreads contamination to adjacent carcass sites. However, washing of carcasses was effective in lowering microbial populations relative to the NTNW treatment. Escherichia coli and coliform counts in all samples were low (0.03 to 0.4 log10 CFU/cm2); however, the mean E. coli or coliform count in NTNW samples was higher (P < 0.05) than those in the rest of the treatments.
ABSTRACT
We evaluated the methods of direct plate count (DPC) on Modified Oxford agar and most probable number (MPN) using Fung-Yu tubes for the detection of natural contamination by Listeria spp. by examining 100 retail samples of raw meat (beef, lamb, pork; and turkey). Listeria monocytogenes was isolated from 10 samples. Other Listeria spp. ( L. innocua , L. murrayi , and L. welshimeri ) were isolated from 27 samples. Despite the fact that very low numbers of Listeria were found on these products, the MPN method was significantly more sensitive than the DPC method. The isolation efficiencies of the MPN and DPC methods were 31 and 17%, respectively. Quantitation of indigenous Listeria showed that many meat samples contaminated with ≤ 4 colony-forming units (CFU) per g tested negative by the DPC method but positive by the MPN method.
ABSTRACT
Subcutaneous and kidney-pelvic-heart fat were trimmed from one side of each beef carcass (n = 9) immediately after cold water washing. Both sides were sampled for aerobic plate counts (APCs) before being moved to the chill room (0 h) and after 72 h of cold storage. The mean APCs (log10 colony-forming units (CFU)/cm2) of trimmed (HFT) sides at 0 or 72 h were not different (P > 0.05) from those of the nontrimmed (NFT) sides. All sides at 72 h had reduced microbial counts compared to 0 h. By 72 h, HFT sides had numerically lower counts than NFT sides, indicating that the microbial reduction effect of the chill temperature may have been greater on fat-trimmed carcasses than on nontrimmed carcasses. Subprimals from HFT and NFT sides that were trimmed to 0.64-cm fat thickness were microbiologically analyzed before (0 days) and after (14 days) vacuum storage. APCs of all subprimals were slightly reduced after 14 d; however, no difference (P > 0.05) occurred in treatment effect. The mean APC was higher for HFT-side subprimals than for NFT-side subprimals at both 0 and 14 days. This difference probably was due to the fat trimming required for NFT-side subprimals at day 0 as compared to minimal or no trimming of HFT-side subprimals. Those HFT subprimals which were not subsequently trimmed may have picked up additional microorganisms from contact surfaces during fabrication. Based on our trimming protocol, although HFT did not show any negative impact on the microbial quality of carcasses, the higher APC of HFT-side subprimals indicated that extensive trimming may not be effective in improving the microbial quality of meat.
ABSTRACT
Beef carcass sides (n = 9 per replicate) were sprayed with water (W), 200 ppm chlorine ©, or 3% (vol/vol) lactic acid (L) immediately after rail inspection and at the end of an 8-h spray-chill cycle, resulting in a total of nine different spray combinations. All treatment combinations involving chlorine and/or lactic acid reduced carcass contamination. The reductions in mean log10 CFU/cm2 for carcass aerobic plate count (APC) data ranged from 0.4 to 1.8. The treatment combination using lactic acid at both spray times (L+L) resulted in the greatest reduction. Additionally, treatment combinations involving lactic acid at either time and in combination with water or chlorine tended to reduce APCs more than those treatment combinations without acid. Browning of blood splashes was observed on carcasses sprayed with lactic acid and persisted until fabrication at 72 h postmortem. A companion study was designed, in conjunction with the carcass decontamination study, to evaluate effect of carcass treatment on the microbiological quality of subprimal subdivisions derived from treated carcasses. A facet of the subprimal study evaluated chlorine spray (200 ppm) and microwave radiation as approaches to improving subprimal shelf life and safety. Cuts taken from sprayed carcasses were vacuum packaged with or without intervention treatments, stored at 1 to 2°C and evaluated for both APC and pathogen populations at specified intervals of up to 120 days. These results demonstrated that neither carcass nor intervention treatment had any significant (P > 0.05), beneficial effect on the microbiological quality of subprimal cuts.
ABSTRACT
One hundred and ninety-five residential refrigerators in Brazos and Robertson counties of Texas were examined for the presence of Listeria monocytogenes . Surfaces on which meat and vegetables were usually stored, as well as other storage areas, were sampled. L. monocytogenes was not recovered from any of the refrigerators sampled. The organism, if introduced, may only be a transient inhabitant of refrigerator surfaces, as long-term colonization of such surfaces does not seem to be a common occurrence.
ABSTRACT
The microbiological effect of hot (55° C), 1% (v/v) lactic acid sprayed on the surface of pork carcasses (n = 36) immediately after dehairing, after evisceration (immediately before chilling) or at both locations in slaughter/ processing was determined. Mean aerobic plate counts (APCs) of all acid-treated carcass surfaces were numerically lower than those of control carcasses: however, in most cases these reductions were not statistically significant (P>0·05). All samples tested for the presence of Salmonella and Listeria were negative. No significant differences in sensory characteristics or microbiological counts were evident for acid-treated and control carcass loins that were vacuum packaged and stored 0-14 days post-fabrication. Mean pH value and scores of sensory attributes such as lean color, surface discoloration, fat color, overall appearance and off-odor of chops from acid-treated carcasses were not significantly and/or consistently different from chops of comparable control carcasses. The role of bacterial attachment to pork skin and its effect on the decontaminating efficiency of lactic acid are discussed.
ABSTRACT
Hot (55°C), dilute (1% v/v) lactic acid was sprayed on beef carcass surfaces immediately after dehiding, after evisceration (immediately before chilling), or at both locations. Surface samples of carcasses were examined for total aerobic plate counts (APCs) and for the presence of Salmonella and Listeria . APCs of treated beef carcasses were lower (P<0.05) than those of control carcasses. APCs were determined both at slaughter day 0 (immediately after carcasses enter the chill room) and after 72 h postmortem. At day 0, reductions in log10 APC by more than 90% occurred when carcasses were treated with lactic acid after evisceration or both after dehiding and after evisceration. The effect of lactic acid decontamination was greatest on carcasses treated with lactic acid both after dehiding and after evisceration. No further reductions in APCs of carcasses were observed on samples taken 72 h postmortem. No difference in color between control and acid-treated carcasses was observed. All samples tested for the presence of Salmonella were negative. Listeria was detected in three samples from control carcasses only. Samples obtained from strip loins of acid-treated or control carcasses did not show any consistent pattern of differences in microbiological counts. Additional data collected from carcasses sprayed with lactic acid in three different sized slaughter plants showed that irrespective of differences in size of slaughter facility, mean APCs of acid-treated carcasses were significantly (P<0.05) lower than those of control carcasses.
