Microbiological profiles of pork carcasses and pork variety meats and decontamination technologies for pork variety meats

Abstract

Experiments were designed and conducted to provide packers, producers, other members of the swine/pork industry and regulatory agencies with information about the microbiological status of pork carcasses and pork variety meats. Collectively, the results offer a snapshot of the occurrence of bacteria on pork carcasses and variety meats collected during only a brief period of time, but provide baseline information for identifying where the industry is and where it should be going in its quest to improve the wholesomeness of products for consumers. Experiment 1 developed microbiological baseline information for pork carcasses using a 3-site sponge sampling protocol. Experiment 2 compared a 3-site sponge sampling protocol with a 2-site sponge sampling protocol as a means for quantifying and characterizing microbiological populations on pork carcasses. Experiment 3 developed microbiological baseline information for 11 pork variety meats (cheek meat, salivary glands, tongues, livers, hearts, kidneys, stomachs, chitterlings, bungs and front feet). Experiment 4 evaluated the effectiveness of 10 decontamination technologies for their ability to reduce bacterial counts on pork variety meats. Experiment 5 evaluated the effectiveness of 7 decontamination technologies for their ability to reduce incidence of Salmonella spp., Listeria monocytogenes and Yersinia enterocolitica on pork variety meats. Results from experiment 1 demonstrated that C. jejuni/coli, with an incidence of 7.9%, was the most commonly found pathogen (of those tested) on pork carcasses in the cooler, followed by L. monocytogenes (5.0%), Salmonella spp. (4.6%) and Y. enterocolitica (0.9%). Mean (log CFU/cm2) APC, TCC and ECC were generally lower (P > 0.05) during the winter, when compared to the summer season. The results of experiment 2 indicated that mean (log CFU/cm2) TCC and ECC did not differ (P > 0.05) between the 3-site sponge sampling protocol and the 2-site sponge sampling protocol at pre-wash, final wash or cooler sampling sites. However, the 2-site sponge sampling protocol was not as effective as the 3-site sponge sampling protocol in detecting Salmonella spp. In the cooler, the 2-site sponge sampling protocol only detected Salmonella spp. at a rate of 2.1% which was less than half of the 4.6% incidence detected using the 3-site sponge sampling protocol. Results of experiment 3 indicated that general microbiological contamination (APC) was relatively high, for most variety meats sampled, with a mean APC ranging between > 4 log CFU/g to < 7 log CFU/g (hearts were the exception, having a mean APC of 3.4 log CFU/g). Mean TCC and ECC ranged between 1.7 to 4.6 and 1.1 to 4.3 log CFU/g, respectively. There were no positive samples of Y. enterocolitica detected on variety meat samples. Less than 1% (4 out of 405) of the samples were positive for C. jejuni/coli. For Salmonella spp., 15% of the samples were positive and a greater number of positive samples were associated with the head (cheek meat, head meat, salivary gland and tongue) and intestinal tract (chitterlings and bung) than with other types of variety meats. Listeria monocytogenes occurred on 16% of samples and the highest incidence rates were associated with variety meat products from the head, the stomach and the front feet. Results from experiment 4 indicated that larger reductions in APC, TCC and ECC on pork variety meats were obtained using trisodium phosphate (12%), acetic acid (2%) and lactic acid (2%) decontamination interventions. Treatments such as hot water (75 to 80°C) or steam resulted in discoloration of red variety meat products due to high temperatures. The hydrogen peroxide (5%) treatment slightly discolored red variety meat products and produced a foam that was undesirable for working/packaging conditions. Results from experiment 5 indicated that lactic acid (2%) immersion was the most successful and consistent decontamination intervention treatment for reducing Salmonella, L. monocytogenes and Y. enterocolitica counts on variety meats tested. Additionally, a 10 sec application of lactic acid (2%) or acetic acid (2%) was more effective than a 5 sec application in reducing Salmonella, L. monocytogenes and Y. enterocolitica.