Listeria Monocytogenes In Pork Research Articles

Characterization and antimicrobial efficacy of active biocomposite containing polylactic acid, oregano essential oil and nisin for pork storage

Traditional packaging made from non-renewable compounds such as petroleum has a negative impact on the environment, which has led to a growing body of research on biodegradable packaging. This paper details the characterization of a biocomposite which was made from cassava bran, coffee husk, and water (BCCW). After this, a layer of polylactic acid (PLA) was added, mixed with nisaplin 1000UI, and 8, 10, 12% concentrations of oregano (Origanum vulgare L) essential oil (OVEO) in order to create an active biocomposite (AB) which could be used as an antimicrobial material in the packaging of pork. In vitro inhibitory effects were evaluated against Listeria monocytogenes, Escherichia coli and Salmonella typhimurium. After obtaining the active biocomposite, the characterization was performed by means of Infrared Spectroscopy (FT-IR), Water Vapor Permeability (WVP), a Mechanical Property analysis, Differential Scanning Calorimetry (DSC), and Scanning Electron Microscopy (SEM). Using the concentration with the highest inhibition against pathogenic bacteria, antimicrobial tests were carried out after the application of the AB in pork meat for 0, 1, 3, 5, and 10 days. Inhibition tests against pathogenic bacteria showed that nisin had a greater effect on Gram positive bacteria, while OVEO had an effect on both Gram positive and Gram negative bacteria. FT-IR analysis allowed for the characterization of the molecular interactions of OVEO and nisin in the matrix compounds of the different biocomposites by identifying and interpreting their respective vibration bands. According to the statistical analysis, the different concentrations of the biocomposites affect WVP (p <0.05). BCCW showed the highest permeability to water vapor, whereas the other treatments did not show significant differences. The mechanical properties test of the AB showed that the different treatments had a significant effect (p <0.05) on the maximum flexural strength and flexural modulus. These values decreased with the application of the PLA layer, the concentrations of the biocomposites did not have a significant maximum deformation effect (p> 0.05). The DSC test on the ABs showed two melting peaks and an increase in the glass transition temperature (Tg) of the PLA, a finding that indicates greater thermal stability in the ABs. SEM images revealed that the nisaplin and OVEO particles were uniformly distributed in the PLA polymer matrix on the surface of the ABs. The ABs showed a significant reduction in Listeria monocytogenes in pork as of day 3 and in the other pathogens as of the 10th day. The biocomposite containing OVEO and nisaplin, showed good potential to be used to food packaging.

The fate and pasteurization-based inactivation of Escherichia coli O157, Salmonella Typhimurium and Listeria monocytogenes in dry, fermented sausages

The fate of main microbial pathogens during production and storage of pork- and beef-based dry fermented sausages was evaluated. The production process resulted in 1.4 log reduction of Salmonella Typhimurium in pork sausages, 1.3 log reduction of Escherichia coli O157 in beef sausages, and 0.8 and 0.5 log reductions of Listeria monocytogenes in pork and beef sausages respectively, compared to initial levels. After 45 days of storage, additional 1.9 log reduction of S. Typhimurium in pork sausages, 1.3 log reduction of E. coli O157 in beef sausages, and 0.9 log reduction of L. monocytogenes in pork, but none in beef, sausages were observed. Furthermore, the potential of pasteurization of finished dry, fermented sausages typical of the meat processing industry in Serbia, to reduce pathogens Salmonella and L. monocytogenes in pork sausages, and E. coli O157 and L. monocytogenes in beef sausages, by using selected temperature-time regimes allowing for subsequent sensory acceptability of the product was evaluated. Overall, the results confirmed that post-processing pasteurization of finished dry fermented sausages has the potential to eliminate Salmonella and E. coli O157 from pork and beef sausages, respectively, while still maintaining acceptable sensory quality of the finished product. However, L. monocytogenes proved to be comparably markedly more heat resistant in both types of sausages, so further research is required to acceptably reduce numbers of this pathogen in dry fermented sausages.

Detection of Listeria monocytogenes in pork and beef using the VIDAS® LMO2 automated enzyme linked immunoassay method

Listeria (L.) monocytogenes, a foodborne pathogen, is known to be a possible contaminant of foods during production and processing. Samples (n=985) of raw meat and by-products obtained from beef and pork were first screened by the VIDAS system for the presence of Listeria spp., followed by testing for the presence of L. monocytogenes. Positive L. monocytogenes results were confirmed by plating on selective agars: 14% of the samples were positive for Listeria and 4% tested positive for L. monocytogenes, of which 3% were confirmed on selective agars. In by-products (17%) the contamination with listeriae was higher than in meat cuts (10%). Only samples strongly positive for Listeria spp. by VIDAS were positive for L. monocytogenes. Overall, the prevalence of L. monocytogenes in beef and pork samples was rather low in comparison to most previous studies. The VIDAS system was shown to be a suitable method for screening out Listeria-negative samples; the main advantage being a markedly reduced assay time.