• Journal of Food Hygiene and Safety
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• v.33 no.4
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• pp.255-258
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• 2018

The objective of this study was to investigate the inhibitory effect of natural antimicrobials on Listeria monocytogenes isolated from Korean slaughterhouses. A mixture of 15 strains of L. monocytogenes at low (3 Log CFU/mL) or high (7 Log CFU/mL) concentration was exposed to various extracts (grapefruit seed extract, citrus fruit extract, ginger extract, pear extract, Japanese apricot concentrate, balloon flower extract, jujube extract, and omija extract) at $0.001-4.0{\mu}g/mL$. Ginger extract, pear extract, Japanese apricot concentrate, balloon flower extract, jujube extract, or omija extract showed no antimicrobial effects on high-concentration of L. monocytogenes (7 Log CFU/mL). However, grapefruit seed extract and citrus fruit extract showed antibacterial effects against L. monocytogenes at 3 and 7 Log CFU/mL with MBCs of 0.001 and $0.002{\mu}g/mL$, respectively. These results indicate that grapefruit seed extract and citrus fruits extract can be used to control L. monocytogenes as natural antimicrobials.

• Journal of Food Hygiene and Safety
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• v.35 no.6
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• pp.552-560
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• 2020

Listeria monocytogenes is a highly pathogenic gram-positive bacterium that is easily isolated from cheese, meat, processed meat products, and smoked salmon. A zero-tolerance (n=5, c=0, m=0/25 g) criteria has been applied for L. monocytogenes in cheese meaning that L. monocytogenes must not be detected in any 25 g of samples. However, there was a lack of scientific information behind this criteria. Therefore, in this study, we conducted a risk assessment based on literature reviews to provide scientific information supporting the baseline and to raise public awareness of L. monocytogenes foodborne illness. Quantitative risk assessment of L. monocytogenes for cheese was conducted using the following steps: exposure assessment, hazard characterization, and risk characterization. As a result, the initial contamination level of L. monocytogenes was -4.0 Log CFU/g in cheese. The consumption frequency of cheese was 11.8%, and the appropriate probability distribution for amount of cheese consumed was a Lognormal distribution with an average of 32.5 g. In conclusion, the mean of probabilities of foodborne illness caused by the consumption of cheese was 5.09×10-7 in the healthy population and 4.32×10-6 in the susceptible population. Consumption frequency has the biggest effect on the probability of foodborne illness, but storage and transportation times have also been found to affect the probability of foodborne illness; thus, management of the distribution environment should be considered important. Through this risk assessment, scientific data to support the criteria for L. monocytogenes in cheese could be obtained. In addition, we recommend that further risk assessment studies of L. monocytogenes in various foods be conducted in the future.

• Journal of Food Hygiene and Safety
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• v.10 no.1
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• pp.7-12
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• 1995

The inhibitory effects of vegetables, collected from Jinju district, on the growth of Listeria monocytogenes were investigated. Among 12 vegerables, garlic, leek, onion and cabbage were remarkably effective to inhibit the growth of the strain. Especially with the addition of extract equivalent 0.25g of raw garlic per ml broth, the population of the strain was decreased wignificantly, and completely inhibited with the addition of 0.625g or more. During the incubation with the addition of extract equivalent 0.25g of raw garlic per ml broth, the degree of inhibition was gradually increased with the lapse of time, and completely inhibited the growth of the strain after 48 hrs. While the pH value of treated broth remained unchanged almost, those of control were slightly reduced.

• Journal of Dairy Science and Biotechnology
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• v.27 no.2
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• pp.43-48
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• 2009

Listeria monocytogenes is a major concern in food processing environments because it is ubiquitous and can easily contaminate food during processing. Contaminated food and the surfaces in food facilities can serve as reservoirs of L. monocytogenes, which can lead to the serious foodborne illness listeriosis in consumers. L. monocytogenes can adhere to materials commonly used in food processing equipment and form biofilms. In the biofilm mode, L. monocytogenes is significantly more resistant to disinfection or sanitizers than its planktonic counterparts. Many researchers have studied the effects of surface materials on bacterial adhesion and the formation of biofilms. Recent studies have focused on preventing the establishment of L. monocytogenes in niches in the food plant environments.

• Microbiology and Biotechnology Letters
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• v.21 no.3
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• pp.200-206
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• 1993

The effect of pH (7, 5 and 4) and nisin (100 and 200IU/ml) on heat resistance of Listeria monocytogenes Scott A were determined using citrate-phosphate buffer system. Heat resistance of vegetative and starved cell was decreased as pH value was lower at 65 and 72C. Starved L. monocytogenes was more resistant than vegetative cell at both temperature. Heat resistance of vegetative and starved cell was decreased significantly with treatment of nisin. The effect of nisin was increased significantly at low pH(5, 4). Adherent microcolony was more resistant to heat and nisin than planktonic cell. Contamination of L. monocytogenes may be prevent by using nisin in food and food processing environments.

• Applied Biological Chemistry
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• v.38 no.4
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• pp.302-307
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• 1995

Four strains of lactic acid bacteria which produced bacteriocins inhibitory to Listeria species were isolated from Kimchi, and were identified as Leuconostoc mesenteroides subsp. mesenteroides (2 strains), Leuconostoc paramesenteroides and Pediococcus pentosaceus. The bacteriocins produced by the isolates inhibited all of the Listeria monocytogenes strains tested, but L. denigrificans 28 and L. welchimeri 89 were not inhibited by the bacteriocin produced by the Leu. paramesenteroides isolate. The bacteriocin produced by the P. pentosaceus isolate was more inhibitory against sensitive strains and showed broader spectrum of antimicrobial activity than those produced by other isolates. The bacteriocins produced by Leuconostoc isolates were sensitive to pronase E treatment, but that produced by the P. pentosaceus isolate was not completely inactivated. The bacteriocins produced by all of the isolates were not sensitive to catalase, ${\alpha}$-amylase and lysozyme and heat (30 min at $100^{\circ}C$) treatments.

• Korean Journal of Food Science and Technology
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• v.29 no.6
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• pp.1236-1240
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• 1997

The crude extract of Morus alba Linne bark which showed strong antimicrobial activity on Listeria monocytogenes was fractionated by some solvents and applied column chromatography for purification of active component. By silica gel column chromatography, active fraction (F-5') was purely isolated and confirmed their strong bactericidal effect on Listeria monocytogenes tested at level of 100 and 300 ppm in tryptic soy broth. The cell wall observed by SEM was abnormal after treatment of F-5'.

• Journal of Food Hygiene and Safety
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• v.23 no.1
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• pp.62-67
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• 2008

Inactivation of Salmonella Typhimurium and Listeria monocytogenenes in mandarin orange, Prunus mume (maesil), and kiwi juices was evaluated. A three-strain mixture of S. Typhimurium or L. monocytogenes was inoculated (7 log CFU/ml) into a commercial mandarin orange juice and maesil juice, and home-maid kiwi extract. The inactivation effect of Maesil juice was estimated by the addition into the other two fruit juices. All fruit juices had acidic pH, ranging from 2.8 to 3.5 and it was not variable during all experimental period, being at $4^{\circ}C$ for 14 days, The present study demonstrated that Maesil juice inactivated throughly L. monocytogenes within 7 days, while kiwi extract and mandarin orange juice archived 3.0-log inactivation and 1.0-log inactivation, respectively, until 14 days of storage. S. Typhimurium was completely reduced by Maesil juice and kiwi extract within 14 days, but mandarin orange juice showed only 1.4-log inactivation. The inactivation of L. monocytogenes and S. Typhimurium was increased by adding 10% maesil juice to both mandarin orange juice and kiwi extract.

• Food Science and Preservation
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• v.11 no.4
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• pp.530-537
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• 2004

This study was conducted to determine the inactivation effect of electrolyzed water and organic acids either alone or in combination on L. monocytogenes or natural microflora on lettuce. Acidic electrolyzed water completely inactivated L. monocytogenes in broth system within 60 sec, but alkalin electrolyzed water caused approximate 1.7 log CFU/g reduction. However, acidic electrolyzed water reduced only 2.5 log CFU/g of L. monocytogenes on lettuce, and similar antimicrobial effect was observed with alkalin electrolyzed water. In the meantime, acidic and alkaline electrolyzed water caused approximately 2 log CFU/g reduction compared to control, whereas both electrolyzed water combined with $1\%$ organic acids ranged from 2.6 to 3.7 log CFU/g reduction. Among the organic acids, both electrolyzed water combined with $1\%$ citric acid showed the strongest synergistic antimicrobial effect to reduce L. monocytogenes on lettuce as well as total counts, yeast and molds. When antimicrobials, alone or in combination were treated into L. monocytogenes inoculated lettuce at $5^{\circ}C\;and\;15^{\circ}C$ for designed periods, the combined alkalin electrolyzed water with $1\%$ citric acid showed the greatest potential to inhibit growth of the bacteria. According to Scanning Electron Microscopy(SEM), the treatment of electrolyzed alkali water in combination with $1\%$ citric acid highly reduced the growth of the L. monocytogenes compared to single treatment and resulted in causing the destruction of cell membrane.

• Journal of Food Hygiene and Safety
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• v.22 no.2
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• pp.132-136
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• 2007

Disinfectants/sanitizers, showing the bactericidal activity of $5log_{10}$ reduction against E. coli ATCC 10536 and Staphylococcus aureus ATCC 6538 used far assessing disinfectants/sanitizers efficacies, were examined whether showing similar efficacies against Salmonella spp. and Listeria monocytogenes, the major food poisoning bacteria, isolated from foods in current Korean market. The bactericidal efficacies on sodium hypochlorite and benzalkonium chloride were assessed by quantitative suspension tests in both 'clean' and 'dirty' conditions, respectively. Test organisms were consisted of E. coli ATCC 10536, Staphylococcus aureus ATCC 6538, Salmonella typhimurium ATCC 13311, Salmonella Enteritidis ATCC 13076, Listeria monocytogenes ATCC 19111, 10 kinds of Salmonella spp. from foods, and 11 kinds of Listeria monocytogenes from foods. More than $5log_{10}$ reduction in viable count for all strains was only achieved with benzalkonium chloride at the tolerance exemption concentration under dirty conditions. However, all strains were achieved more than $5log_{10}$ reduction under clean conditions.