The antimicrobial activity of mustard extract containing allyl isothiocyanate (AIT), the major pungent component, against Yersinia enterocolitica and Listeria monocytogenes, which are known as low temperature growth bacteria, was determined by gaseous contact. The minimal inhibitory concentration (MIC) for AIT to both bacterial cells was examined by incubation in glass jars with different concentrations of AIT. The MIC of AIT to injure these bacterial cells was also studied. The MIC of AIT against Y. enterocolitica was found to be 14 ppm at 10°C, 45ppm at 20°C, 68 ppm at 30°C and 36 ppm at 40°C. The MIC of AIT against L. monocytogenes was found to be 14 ppm at 10°C, 71 ppm at 20°C, 98 pp mat 30°C and 145 ppm at 40°C . Since the MIC of AIT to both bacterial cells at 10°C was low, AIT is considered effective for low temperature growth bacteria at low temperature. With injured bacterial cells, the MIC of AIT to log-phase and dead-phase cells of Y. enterocolitica was 20 ppm at 30°C, that to log-phase and dead-phase cells of L. monocytogenes was found to be 43 ppm and 68 ppm at 30°C, respectively. From these findings, AIT is more effective for injured bacterial cells than uninjured cells.
A bacteriocin of Pediococcus acidilactici K1 isolated from natural dry fermented sausage inhibited the growth of Listeria monocytogenes in the fermented sausage. The bactericidal effects of P. acidilactici K1 exhibited initial 5.8 to 0 log cycle during fermenting after a 14 days. When minced pork meat with bacteriocin powder (3, 000, 7, 000 and 15, 000 AU/g) treated from 10% skim milk was mixed at 6°C, the growth of L.monocytogenes was was inhibited, but Salmonella Enteritidis and Staphylococcus aureus were not. Simultaneously, bacteriocin powder (500 AU/ml) inhibited the growth of L.moncytogenes at 32°C in MRS broth. These results confirmed the presence of bacteriocin of P. acidilactici K1 in these foods.