Gwang-Hee Kim

Synergetic effect of combined fumaric acid and slightly acidic electrolysed water on the inactivation of food-borne pathogens and extending the shelf life of fresh beef.

To evaluate synergetic effect of slight acidic electrolysed water (SAEW) and fumaric acid (FA) on inactivation of total viable count (TVC) and Staphylococcus aureus, Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella Typhimurium in fresh beef and to study shelf life and sensory quality of beef.

Evaluation of the performance of the IQ-Check kits and the USDA Microbiology Laboratory Guidebook methods for detection of Shiga toxin-producing Escherichia coli (STEC) and STEC and Salmonella simultaneously in ground beef

To evaluate the performance of the IQ‐Check kits and the USDA Microbiology Laboratory Guidebook (MLG) methods for detection of the top seven Shiga toxin‐producing Escherichia coli (STEC) (O157:H7, O26, O45, O103, O111, O121 and O145) in ground beef and both STEC and Salmonella in co‐inoculated samples.

Analysis of Transfer Rate on Listeria monocytogenes Contaminated Pork Meat During Processing

In this study, the transfer rate of wild type Listeria monocytogenes (LM) was investigated to estab- lish the standard of safety management during pork meat processing for meat to meat and meat to food contact sur- faces contamination at 5 and 10 o C. The transfer rate of LM from meat to meat during the processing increased from 0.02% after 30 min to 0.42% after 120 min at 5 o C, while for conveyor belt and stainless steel, it decreased from 0.015% and 0.013% after 30 min to 0.002% and 0.0003% after 120 min at 5 o C, respectively (p < 0.05). When temper- ature increased to 10 o C, the transfer rates of LM from meat to meat, conveyor belt and stainless steel were the highest at 60 min exposure, and all decreased after 120 min. In reverse, the transfer rate from food contact surface to pork meat was significantly higher than that from pork meat to food contact surface (p < 0.01). Also, the transfer rate to con- veyor belt was significantly higher than stainless steel (p < 0.05) and it was highest at 30 min exposure time in both 5 and 10 o C. This study indicates that the transfer and adherence rates of LM are influenced by the contact time and tem- perature. Consequently, these results were utilized to develop a predictive model with a high level of confidence which can lead to prevent cross-contamination during pork meat processing.

Analysis of Microbiological Contamination Levels of Cabbage and Fresh-cut Produce on Difference Area toward Climate in Korea

ABSTRACT - The purpose of this study was to evaluate microbiological contamination of fresh-cut produce sal-ads and raw cabbage toward climate change. Total aerobic bacteria, coliform and Escherichia coli were monitored toget the contamination levels and E. coli O157:H7, Staphylococcus aureus, Bacillus cereus, Listeria monocytogenesand Salmonella spp. to detect pathogens with risk of foodborne disease from samples. Collection of 360 samples (180fresh-cut produce salads and 180 raw cabbage), including 60 samples from each area after setting 3 areas dependingon annual temperature and annual rainfall. As a result, total aerobic bacteria and coliform group were different wasperformed areas in raw cabbage but there was no difference between areas in fresh-cut produce salads. In additionfoodborne pathogens including E. coli were not isolated from fresh-cut produce salads.Key words: Fresh-cut produce, Foodborne pathogens, Contamination levels, Climate 최근 전 세계적으로 민감한 문제 중 하나인 기후변화는기후 온난화, 대기 오염 증가로 인하여 생태계는 물론, 경제, 산업, 문화의 전반적인 부분에 걸쳐 다양한 파급효과가발생하고 있는 실정이며 식품 안전을 포함한 사회 전반의문제가 되고 있다. 이에 세계적 규모의 기후변화는 이제 현실화되어 심각한 문제를 야기하고 있으며, 기후변화에 따른 문제점이 특정 국가 차원에서 국제적으로 확대되고 있다

Genome Sequences of 34 Shiga Toxin-Producing Escherichia coli Isolates from Swine and Other Sources

ABSTRACT Shiga toxin-producing Escherichia coli (STEC) bacteria are foodborne pathogens that can be carried by various animals. The swine STEC population is partially composed of host-specific strains that are often not well characterized. In this work, the genome sequences of a number of swine STEC strains are presented.

Escherichia coli O157:H7 Acid Sensitivity Correlates with Flocculation Phenotype during Nutrient Limitation

Shiga toxin producing Escherichia coli (STEC) strains vary in acid resistance; however, little is known about the underlying mechanisms that result in strain specific differences. Among 25 STEC O157:H7 strains tested, 7 strains flocculated when grown statically for 18 h in minimal salts medium at 37°C, while 18 strains did not. Interestingly, the flocculation phenotype (cells came out of suspension) was found to correlate with degree of acid sensitivity in an assay with 400 mM acetic acid solution at pH 3.3 targeting acidified foods. Strains exhibiting flocculation were more acid sensitive and were designated FAS, for flocculation acid sensitive, while the acid resistant strain designated PAR for planktonic acid resistant. Flocculation was not observed for any strains during growth in complex medium (Luria Bertani broth). STEC strains B201 and B241 were chosen as representative FAS (2.4 log reduction) and PAR (0.15 log reduction) strains, respectively, due to differences in acid resistance and flocculation phenotype. Results from electron microscopy showed evidence of fimbriae production in B201, whereas fimbriae were not observed in B241.Curli fimbriae production was identified through plating on Congo red differential medium, and all FAS strains showed curli fimbriae production. Surprisingly, 5 PAR strains also had evidence of curli production. Transcriptomic and targeted gene expression data for B201 and B241indicated that csg and hde (curli and acid induced chaperone genes, respectively) expression positively correlated with the phenotypic differences observed for these strains. These data suggest that FAS strains grown in minimal medium express curli, resulting in a flocculation phenotype. This may be regulated by GcvB, which positively regulates curli fimbriae production and represses acid chaperone proteins. RpoS and other regulatory mechanisms may impact curli fimbriae production, as well. These findings may help elucidate mechanisms underlying differences among STEC strains in relating acid resistance and biofilm formation.

Combination of Slightly Acidic Electrolyzed Water, Ultrasound and Water Wash to Maximize the Sanitization Effect against Microbial Contamination on Lettuce

Microbial contamination of fresh produce is still a major concern to the food industry regardless of all recent improvements in food safety technologies. Among the numerous technologies used slightly acidic electrolyzed water (SlAEW) and ultrasound, are both known as environmental friendly technologies. Although, SlAEW still needs more improvement to be used in food sanitization and ultrasound alone does not effectively reduce microbial numbers in food samples. Hence, the aim of this study was to develop an improved hurdle for fresh produce sanitization using combined treatments of SlAEW (pH 5.4, available chlorine concentration 22 mg/L, oxidation reduction potential 544-592 mV) with ultrasound. Lettuce samples were treated with distilled water (DW), SlAEW, SlAEW followed by water wash (SlAEW + WW), SlAEW with ultrasound (SlAEW + US) and SlAEW with ultrasound followed by water wash (SlAEW + US + WW) at room temperature (24 ± 2 °C), respectively. Following treatments, number of yeasts and molds (YM), total bacteria (TBC) and artificially inoculated Escherichia coli O157:H7 were enumerated. The results showed that ultrasound and water wash alone did not significantly increase the sanitation efficacy of SlAEW. However, treatment of the sample with SlAEW and ultrasound simultaneously, followed by water wash (SlAEW + US + WW) resulted in a great enhancement in microbial reduction. This combined treatment resulted in the reduction of 3.7, 4.1 and 3.8 log CFU/g in YM, TBC and E. coli O157:H7 respectively. Therefore, there is a great chance that this simple hurdle technology can be used in fresh produce as well as other types of food industry to improve the safety of product. Furthermore, addition of mild heat or other treatments should be investigated. This can result in higher numbers of microbial inactivation with cheap, easy to operate and environmental friendly technology.