• Journal of Food Hygiene and Safety
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• v.34 no.2
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• pp.170-177
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• 2019

The aim of this study was to investigate the effect of different concentrations of chlorine dioxide ($ClO_2$) on sterilization and deodorization of food-holding cabinets under different exposure times. For the measuring sterilization and deodorization, a 6.5 L chamber and a 625 L cabinet with circulation systems were used. Two bacteria (Staphylococcus aureus KCTC1916 and Escherichia coli KCTC 1682) that were artificially inoculated in the plate respectively were put into the 6.5 L chamber and the 625 L cabinet. The $ClO_2$ gas was produced by ampules. In the 6.5 L chamber, neither of the two bacteria was detected after 24 hours treatment by $ClO_2$ gas. Moreover, the deodorization rate against ammonia and phenol was 94% and 70%, respectively, but deodorization against formaldehyde was not effective. When the concentration reached maximum (6 ampule, 4.6 ppm) levels in the cabinet, it lasted for approximately 2 h and then decreased slowly. When a circulator was used, the gas concentration was very low (6 ampule, 0.8 ppm) and the antibacterial activity against S. aureus and E. coli was low. The level of reduction against S. aureus and E. coli was 2.98 log CFU/plate and 6.06 log CFU/plate, respectively, in the cabinet after 24 h without a circulator. The reduction against S. aureus KCTC1916 and E. coli KCTC1682 was 2.69 log CFU/plate and 4.41 log CFU/plate for 24 h, respectively.

• Journal of Food Hygiene and Safety
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• v.37 no.2
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• pp.97-106
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• 2022

Listeria monocytogenes (L. monocytogenes) is one of gram-positive foodborne pathogens with a very high fatality rate. Unlike most foodborne pathogens, L. monocytogenes is capable of growing at low temperatures, such as in refrigerated foods. Thus, various physical and chemical prevention methods are used in the manufacturing, processing and distribution of food. However, there are limitations to the methods such as possible changes to the food quality and the consumer awareness of synthetic preservatives. Thus, the aim of this study was to evaluate the anti-listeria activity of lactic acid bacteria (LAB) isolated from kimchi and characterize the bacteriocin produced by Lactococcuslactis which is one of isolated strains from kimchi. The analysis on the anti-listeria activity of a total of 36 species (Lactobacillus, Weissella, Lactobacillus, and Lactococcus) isolated from kimchi by the agar overlay method revealed that L. lactis NJ 1-10 and NJ 1-16 had the highest anti-listeria activity. For quantitatively analysis on the anti-listeria activity, NJ 1-10 and NJ 1-16 were co-cultured with L. monocytogenes in Brain Heat Infusion (BHI) broth, respectively. As a result, L. monocytogenes was reduced by 3.0 log CFU/mL in 20 h, lowering the number of bacteria to below the detection limit. Both LAB strains showed anti-listeria activity against 24 serotypes of L. monocytogenes, although the sizes of clear zone was slightly different. No clear zone was observed when the supernatants of both LAB cultures were treated with proteinase-K, indicating that their anti-listerial activities might be due to the production of bacteriocins. Heat stability of the partially purified bacteriocins of NJ 1-10 and NJ 1-16 was relatively stable at 60℃ and 80℃. Yet, their anti-listeria activities were completely lost by 60 min of treatment at 100℃ and 15 min of treatment at 121℃. The analysis on the pH stability showed that their anti-listeria activities were the most stable at pH 4.01, and decreased with the increasing pH value, yet, was not completely lost. Partially purified bacteriocins showed relatively stable anti-listeria activities in acetone, ethanol, and methanol, but their activities were reduced after chloroform treatment, yet was not completely lost. Conclusively, this study revealed that the bacteriocins produced by NJ 1-10 and NJ 1-16 effectively reduced L. monocytogenes, and that they were relatively stable against heat, pH, and organic solvents, therefore implying their potential as a natural antibacterial substance for controlling L. monocytogenes in food.