• Korean Journal of Agricultural Science
• /
• v.50 no.3
• /
• pp.417-425
• /
• 2023

Because an irradiation of 405 nm violet light could have a strong energy, it was used to be sterilized against various microbes in the indoor air condition or fresh food. Escherichia coli is a representative bio-pollutant in the indoor air-borne bacteria, and a hygienic microbe in the horticultural food. This study evaluated the inactivation influences on E. coli DS5α after exposure to 405 nm violet-light (VL) by investigating irradiating time, and the vertical and horizonal distance from light source. The illumination of 405 nm VL was inversely proportional to the distance from the VL source. E. coli DS5α on nutrient agar (NA) was inactivated approximately 50% more than the control when irradiated at 65 cm from 405 nm VL for 3 hours. When compared to the control, E. coli DS5α was inactivated approximately 50% within 70 cm from 405 nm VL for 3 hours. As it was irradiated for 3 hours 70 cm away from 405 nm VL, the horizonal distance from the point was negatively correlated to the inactivation of E. coli DS5α. These results indicated that the inactivation of E. coli DS5α grown on NA medium needs to be irradiated with 405 nm within 70 cm from the light source for 3 hours.

• Journal of Food Hygiene and Safety
• /
• v.13 no.2
• /
• pp.112-120
• /
• 1998

This study was performed to investigate the synergistic effect of chitosan and sorbic acid as a new food preservative. So it was performed to investigate inhibitory effect on growh of E. coli 0157:H7, gram negative pathogenic food borne disease bacteria and of S. aureus, gram positive food borne disease bacteria in chitosan, sorbic acid and combination of chitosan and sorbic acid. Minimun Inhibitory Concentration (MIC) of chitosan in E. coli 0157:H7 was 500 ppm at pH 5.0, 250 ppm at pH 5.5, 500 ppm at pH 6.0, and 2000 ppm at pH 6.5, while in Staph. aureus 31.25 ppm at pH 5.0 and 62. 5 ppm at more than pH 5.5. also, MIC of sorbic acid in E. coli 0157:H7 was 500 ppm at pH 5.0, 1500 ppm at pH 5.5, and 2000 ppm at more than pH 6.0, while in Staph. aureus 1500 ppm at pH 5.0 and more than 2000 ppm at more than pH 5.5. Due to the effect of pH in E. coli 0157:H7, MIC of combined chitosan and sorbic acid was 500 ppm of chitosan with 500 ppm of sorbic acid at pH 6.5, but 250 ppm of chitosan with 31.3 ppm of sorbic acid at pH 5.0. In Staph. aureus, there was great effect of chitosan, but neither effect of pH nor sorbic acid. When E. coli 0157:H7 were treated with 500 ppm of chitosan with 500 ppm of sorbic acid and 250 ppm of chitosan with 250 ppm of sorbic acid at pH 6.5, they were inhibited. But, they were increased at the initial concentration of bacteria at 1000 ppm of chitosan in 18 hours, at 500 ppm of chitosan in 36 hours. There was no effect of growth inhibition with sorbic acid but great effect with chitosan on Staph. aureus. The correl~tions between MICs of chitosan and sorbic acid in E. coli 0157:H7 accoding to pH were higher than those in Staph. aureus. R values in E. coli 0157:H7 were 0.95 (p<0.01), 0.99 (p<0.01), 0.97 (p<0.01), and 0.99 (p<0.01) at pH 6.5, 6.0, 5.5, and 5.0 respectively. The synergistic effect of chitosan and sorbic acid in E. coli 0157:H7 could be confirmed from the result of this experiment. Therefore, it was expected that the food preservation would increase or maintain by using sorble acid together with chitosan, natural food additive that did no harm to human body.

• Journal of Food Hygiene and Safety
• /
• v.28 no.3
• /
• pp.279-285
• /
• 2013

To establish sample preparation method for detection of food-borne pathogens from lettuce, perilla leaves, cucumber, pepper, and cherry tomato, the influences of diluent composition, processing time, and proportion of diluent to sample were examined. Each produce was inoculated with 6.0 log $CFU/cm^2$ of Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus. Each produce was treated with 0.1% peptone water, and D/E neutralizing broth. Processing time of produce was 30, 60, 90, and 120s, and the proportion of diluent to sample was 2 : 1, 4 : 1, 9 : 1, and 19 : 1. The number of bacteria after treatment of D/E neutralizing broth was higher than that of 0.1% peptone water (P<0.05). In cherry tomato, the population of S. typhimurium recovered from treated with D/E broth was higher than that recovered from treated with 0.1% peptone water by 1.05 log $CFU/cm^2$ (P<0.05). No difference in numbers of pathogens was observed in processing time. Optimum proportion of diluent to perilla leaf, iceberg lettuce, cucumber, green pepper, and tomato was 9 : 1, 4 : 1, 2 : 1, 2 : 1, and 2 : 1, respectively. These data suggest that D/E neutralizing broth should be recommend as diluent, and the diluent volume applied to produce should be determined in proportion to produce surface area per weight (g).

• Journal of Food Hygiene and Safety
• /
• v.30 no.4
• /
• pp.309-314
• /
• 2015

The purpose of this study is to monitor the microbial contamination of ice collected from food stores or restaurants from all over the country. From the ice collected on a regional basis, it was observed that the average number of total aerobic bacteria (TAB) of samples from Seoul was the highest, showing 2.31 log CFU/g, while that of samples from Jeolla-do was the lowest, showing 1.83 log CFU/g. The food-borne pathogens (Staphylococcus aureus, Listeria monocytogenes) were not detected from the ice. Also the average number of TAB of packaged ice (commercial ice) was 0.45 log CFU/g lower than that of ice from ice-making machine. Among three types of stores (the bakery, the dessert store and the beverage store), ice from dessert store showed the highest number of TAB (2.37 log CFU/g). This study suggests that the hygienic management of the ice from the stores is necessary. Therefore, to ensure the hygienic management of ice, not only the ice-making machine should be sanitized on a regular basis but also a thorough individual hygiene is required from food manufacturing workers.

• Microbiology and Biotechnology Letters
• /
• v.40 no.2
• /
• pp.144-151
• /
• 2012

In the course of this study aimed at the development of functional food ingredients from seaweeds, the in vitro antimicrobial activities of methanol extracts prepared from 35 different seaweeds (17 phaeophyta, 11 rhodophyta and 7 chlorophyta) were determined against food-borne diseases and pathogenic microorganisms including multi-drug resistant (MDR) Pseudomonas sp. and Candida sp. Based on disc-diffusion assays at 500 g/disc concentration of the methanol extracts, Ishige okamurai, I. foliacea, Sargassum confusum, and S. yamade exhibited strong antibacterial activities in a broad-spectrum, except against Pseudomonas aeruginosa. In addition to the latter four seaweeds, Ecklonia stolonifera, E. cava and Eisenia bicyclis also demonstrated antifungal activity against C. albicans. Among these 8 selected seaweeds, I. okamurai, I. foliacea, and S. yamade exhibited strong hemolytic activity (55-93%) at 500 g/ml against human RBC. Organic solvent sequential fractions using hexane, ethylacetate and butanol, and water residues were prepared from the 8 selected seaweeds and their anti-Candida sp. activities were further determined. The ethylacetate and butanol fraction of I. okamurai, and the hexane fraction of I. foliacea demonstrated antifungal activity against MDR-pathogenic Candida sp. Although the solvent fractions had no activity against MDR-Pseudomonas sp., our results suggest that seaweeds, especially Ishige okamurai, I. foliacea, S. confusum, and S. yamade could be developed as broad-spectrum antimicrobial ingredients.

• The Korean Journal of Food And Nutrition
• /
• v.28 no.4
• /
• pp.728-736
• /
• 2015

Cronobacter species (Cronobacter spp.), previously known as Enterobacter sakazakii, are gram negative food borne pathogenic bacteria. They pose a very high risk of infection to neonates and immuno-compromised individuals and can affect the human central nervous system. Consequently, survivors often suffer from severe neurological impairment including hydrocephalus, quadriplegia, and developmental delays. Cronobacter spp. were not only isolated from plant food and products such as cereals, fruits, vegetables, legume products, herbs, and spices but also from animal source foods such as milk, meat, fish, and products made from these foods. Therefore, rapid detection of Cronobacter spp. is essential for food safety. Many detection methods have been developed since the Cronobacter spp. were first reported. However, the development of more rapid, sensitive, and easy-to-use detection methods for the Cronobacter spp. is required. In this review, our aim was to study and compare the available detection methods for Cronobacter spp., including culture-based, molecular biology-based, and immunology-based methods. This study will contribute to the development of new and rapid detection method for Cronobacter spp.

• Journal of Environmental Health Sciences
• /
• v.45 no.5
• /
• pp.434-442
• /
• 2019

Objectives: This study was performed in order to report the epidemiological features of a food poisoning outbreak caused by multiple pathogens in a high school in Chungcheongnam-do Province, Korea in April 2019 and to suggest measures to prevent a similar incidence. Methods: A total of 39 patients with diarrhea were examined. Environmental samples were obtained from 6 food handlers, 4 food utensils, 72 preserved foods served during the food poisoning outbreak, 9 door handles, 10 drinking water samples from water dispensers, and 6 ground water samples from water taps. These analyzed to detect viruses and bacteria. Results: Among the 39 patients, 21 cases (53.8%) of enteroaggregative E. coli (EAEC), 7 cases of Staphylococcus aureus (17.9%), and 17 cases of norovirus (43.6%) were positive, and in 16 of the cases a co-infection with at least one other pathogen were observed. EAEC was assumed to be transmitted from contaminated drinking water because it was also detected in the water sample from a water dispenser in the dormitory. Staphylococcus aureus was isolated only in the fecal samples of patients, meaning it was not possible to trace its origin. The genotype of norovirus detected in the drinking water and ground water was consistent with that isolated from patients, and it was determined that the norovirus infection originated from the school's water environment. Conclusions: These findings indicate that a lack of environmental hygiene management related to school meals caused the food poisoning incident. In particular, a lack of management of drinking water, water supply, and personal hygiene should be pointed out. This should be urgently addressed and continuous monitoring should be carried out in the future. In addition, students and staff should be educated and trained to improve their personal hygiene.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.38 no.2
• /
• pp.252-260
• /
• 2009

Whereas the numbers of childcare centers and kindergartens are increasing rapidly, systematic management to control the food safety of foodservice operation is not yet well established. Samples from 12 centers in Seoul and Gyeonggi Province were collected to assess the microbiological quality of 32 raw materials, 24 cooked foods, 76 food-contact surfaces (knives, cutting boards, dish towels and gloves), 17 employees' hands and 12 air-borne bacteria. The microbiological analyses were performed for aerobic plate counts (APC), Enterobacteriaceae, E. coli and 7 pathogens (B. cereus, C. jejuni, C. perfringens, L. monocytogenes, Salmonella spp., S. aureus, and V. parahaemolyticus). Among raw materials, E. coli ($1.39{\sim}2.08\;\log\;CFU/g$) were detected in 4 out of 6 meats and 7.46 log CFU/g of APC in tofu. High enterobacteriaceae levels of 4.23, 5.14 and 4.19 log CFU/g were found in cucumber salad, steamed spinach with seasonings and steamed bean sprout with seasonings, respectively. No pathogens were found in all samples except for C. perfringens detected from raw spinach and raw lotus root. Only APC and enterobacteriaceae were found in food-contact surfaces. Two of the 23 knives and three of the 24 kitchen boards showed over 500 CFU/$100\;cm^2$ of APC; also, APC levels (5.03 to 5.44 log CFU/g) were detected in 4 of the 12 dish towels. Only one glove showed Enterobacteriaceae (2.44 log CFU/glove) contamination. Enterobacteriaceae were found in 2 employees' hands ($2.37{\sim}4.44\;\log\;CFU$/hand) among the 16 employees. The contamination levels of air-borne bacteria were shown unacceptable in two (2.25 and 2.30 log CFU/petri-film/15 min) out of the 12 kitchen areas. These results suggest that the microbiological hazards in some foods and environments are not well controlled and thus a guideline should be provided to ensure the food safety in childcare center and kindergarten foodservice operations.

• Journal of Life Science
• /
• v.33 no.10
• /
• pp.842-850
• /
• 2023

Pyrrolnitrin, pyrrolomycin, and pyoluteorin are functional halogenated phenylpyrrole derivatives (HPDs) derived from microorganisms with diverse antimicrobial activities. Pyrrolnitrin is a secondary metabolite produced from L-tryptophan through four-step reactions in Pseudomonas fluorescens, Burkholderia cepacia, Serratia plymuthica, etc. It is currently used for the treatment of superficial dermatophytic fungal infections, has high antagonistic activities against soil-borne and foliar fungal infections, and has many industrial applications. Since pyrrolnitrin is easily decomposed by light, it is difficult to widely use it outdoors. As an alternative, fludioxonil, a synthetically produced non-systemic surface fungicide that is structurally similar and has excellent light stability, has been commercialized for seed and foliar treatment of plants. However, due to its high toxicity to aquatic organisms and adverse effects in human cell lines, many countries have established maximum residue levels and strictly control its levels. Pyrrolomycin and pyoluteorin, which have antibiotic/antibiofilm activity against Gram-positive bacteria and high anti-oomycete activity against the plant pathogen Pythium ultimum, respectively, were isolated and identified from microorganisms. This review summarizes the biosynthesis and production of natural pyrrolnitrin derived from bacteria and the characteristics of synthetic fludioxonil and other natural phenylpyrrole derivatives among the HPDs. We expect that a plethora of highly effective, novel HPDs that are safe for humans and environments will be developed through the generation of an HPD library by microbial biosynthesis and chemical synthesis.

• Journal of Food Hygiene and Safety
• /
• v.35 no.5
• /
• pp.468-476
• /
• 2020

We aimed to analyze the microbiological quality of the ready-to-eat (RTE) side dishes collected from traditional markets, supermarkets, and cafeterias in Gyeonggi-do in 2019. A total of 108 samples were analyzed for total aerobic bacterial counts, coliforms and foodborne pathogens depending on place of purchase and cooking methods. Results show that Bacillus cereus was detected in 14 (12.9%) out of 108 samples of side dishes, while no other foodborne pathogens were detected. The mean detected level (range) of total aerobic bacteria depending on place of purchase was 5.8 log CFU/g (3.0 to 8.2 log CFU/g) for traditional markets, 4.3 log CFU/g (2.4 to 7.8 log CFU/g) for supermarkets, and 3.80 log CFU/g (0.0 to 6.8 log CFU/g) for cafeterias, indicating that there was a significant (P<0.05) difference in total aerobic bacterial counts among places of purchase. Among the samples, the highest counts of total aerobic bacteria and coliforms were detected in saengchae (raw vegetables), followed by namul (seasoned herbs, vegetables), bokkeum (stir-fried foods), and jorim (foods cooked in soy sauce). The growth of total aerobic bacteria in seasoned soybean sprouts was inhibited when the sprouts were stored at 4℃ up to 24 h, whereas bacteria rapidly grew at 20 and 35℃ after 3 and 6 h, respectively. These results reveal that storage temperature might play a significant role for the microbiological quality of seasoned soybean sprouts when they are sold in markets. Thus, this study suggests that RTE side dishes should be stored at refrigerated temperature when being sold at markets as well as after purchasing to improve their microbiological quality.