Joon-Il Cho

Microbiological Contamination Levels in the Processing of Korea Rice Cakes

This study was conducted to evaluate microbial contamination levels of Korea traditional rice cakes such as Sirutteok, Garaetteok and Gyeongdan in the manufacturing process and environment. The microbial contamination levels such as total aerobic bacteria, fungi, coliforms, Escherichia coli, Staphylococcus aureus, Bacil- lus cereus and Clostridium perfringens of rice cake products were analyzed. The contamination levels of total aerobic bacteria, coliforms, fungi and B. cereus in raw materials were in the range of 2.4~4.5, ND~1.9, 1.2~2.1 and 1.0~2.1 log CFU/g, respectively. The microbial contamination levels of total aerobic bacteria, coliforms, fungi and B. cereus in manufacturing process of rice cakes were increased in the soaking and grinding steps and were decreased in steaming step. E. coli, S. aureus and C. perfringens were not detected in any manufacturing process and environment. The microbial contamination levels of raw materials and final products of rice cake were suitable for microbial safety standard in Korea. However, the manufacturing environment such as equipments and employees sanitation were in trouble for microbial safety. The results of this study suggest that safety education for personal hygiene and safety management in processing environment are continuously required to assure safety in working environment and employees individual hygiene.

Characterization of pathogenic Escherichia coli strains linked to an outbreak associated with kimchi consumption in South Korea, 2012

Pathogenic Escherichia coli (PEc) is a leading cause of both foodborne and waterborne illness. In September 2012, a major foodborne outbreak with PEc occurred, affecting approximately 1,200 students and food handlers from 7 schools in Gyeonggi province, South Korea caused by contaminated kimchi. For detection of PEc in kimchi, real-time polymerase chain reaction (RT-PCR) and traditional culture methods were used. EAEC and ETEC genotypes were identified in samples from individuals with the illness and in kimchi using conventional PCR. Bacteria in stool samples were genetically similar to bacteria from kimchi (98% homology). PEc from kimchi was identified as the causative agent of a foodborne outbreak in South Korea. A significant link between kimchi and individuals with foodborne illnesses after consuming kimchi was demonstrated.

An Analysis of Epidemiological Investigation Reports Regarding to Pathogenic E. coli Outbreaks in Korea from 2009 to 2010

ABSTRACT - Recently pathogenic E. coli is one of the main foodborne pathogens resulting in many patients inKorea. To understand the characteristics of pathogenic E. coli outbreaks in Korea, the epidemiological investigationreports of pathogenic E. coli outbreak in 2009 (41 reports) and in 2010 (27 reports) were collected in the web site ofthe Korea Centers for Disease Control and Prevention, reviewed and analysed in this study. The main places of thepathogenic E. coli outbreaks were food catering service area (64.8%) and restaurants (25.0%). The main type of thepathogens were EPEC (44.7%) and ETEC (34.2%). EAEC and EHEC was responsible for 10.5 and 9.2%, respec-tively. Eight of 68 outbreak cases were caused by more than 2 types of pathogenic E. coli which implicates the com-plicated contamination pathways of pathogenic E. coli . The incidence rate of pathogenic E. coli was 33.6 ± 30.5% andthe main symptoms were diarrhea, stomach ache, nausea, vomiting, and fever etc. The two identified food sourceswere identified as frozen hamburger pattie and squid-vegetable mixture. To improve the food source identification byepidemiological investigation, food poisoning notification to the agency should not be delayed, whole food itemsattributed the outbreak should be collected and detection method of the various pathogenic E. coli in food has to beimproved. In conclusion, the characteristics between the EHEC outbreaks in the western countries and the EPEC orETEC outbreaks in Korea needs to be distinguished to prepare food safety management plan. In addition, the devel-opment of the trace back system to find the contamination pathway with the improved detection method in food andsystemic and cooperative support by the related agencies are necessary. Key words: pathogenic E. coli outbreak, epidemiological investigation, Korea, characteristic analysis.

A Monitoring for the Management of Microbiological Hazard in Rice-cake by Climate Change

This study was conducted to investigate the microbiological contamination levels in rice cakes and rice flour due to climate change in three areas classified to their temperature and precipitation. We investigated the contamination levels of total aerobic bacteria, coliforms, Escherichia coli, Bacillus cereus, Staphylococcus aureus, Clostridium perfringens of rice flour and 3 rice cakes such as Garaetteok, Sirutteok and Gyeongdan. Contamination levels of total aerobic bacteria in rice flour were 4.9 log CFU/g. In a total of 70 rice flour, yeasts & molds and coliforms were detected in 42 and 52 samples at the levels of 43 CFU/g and 1.29 log CFU/g, respectively. S. aureus were detected in only 1 rice flour (1.66 log CFU/g) out of 70. In an investigation of contamination levels in rice cakes, the population of total aerobic bacteria were highest in Gyeongdan (5.18 log CFU/g) and coliforms were highest in Gareattock (2.93 log CFU/g). There was no detection of E. coli and B. cereus except for only 1 Gareattock (1.20 log CFU/g). There were no differences of contamination levels among the three areas. If constant monitoring of rice cakes and rice flour is conducted on the basis of this study, it is expected to be able to analyze the change of con- tamination levels in rice cakes and rice flour due to climate change.

Occurrence of pathogenic Escherichia coli in commercially available fresh vegetable products in Korea

Pathogenic E. coli is a major foodborne pathogen associated with gastroenteritis worldwide. Fresh vegetable products as well as raw meat and meat products have been recognized as important modes of transmission within the foodborne route. The objective of the present study was to determine the presence of six virulence factors (stx1, stx2, lt, st, eaeA, and ial) in E. coli isolated from fresh vegetable products to provide information on risk assessment of pathogenic E. coli in Korea. From 416 collected samples, including vegetable salad mix, sprouts, baby leaf vegetables, and unpasteurized fruit and vegetable juices commercially available in Korea, a total of 30 samples were positive for E. coli strains, resulting in an overall prevalence of 7.2%. Of the 120 E. coli isolates, only one isolate (0.8%), which was obtained from unpasteurized fruit and vegetable juices, was confirmed to possess the eaeA gene, but lacked stx genes. This study showed that some fresh vegetable product samples were contaminated with enteropathogenic E. coli.

Identification of a Novel Small Molecule Inhibitor Against SARS Coronavirus Helicase.

A new chemical inhibitor against severe acute respiratory syndrome (SARS) coronavirus helicase, 7-ethyl-8-mercapto-3-methyl-3,7-dihydro-1H-purine-2,6-dione, was identified. We investigated the inhibitory effect of the compound by conducting colorimetry-based ATP hydrolysis assay and fluorescence resonance energy transfer-based double-stranded DNA unwinding assay. The compound suppressed both ATP hydrolysis and double-stranded DNA unwinding activities of helicase with IC50 values of 8.66 ± 0.26 μM and 41.6 ± 2.3 μM, respectively. Moreover, we observed that the compound did not show cytotoxicity up to 80 µMconcentration. Our results suggest that the compound might serve as a SARS coronavirus inhibitor.

Effects of Temperature and Packaging on the Growth Kinetics of Clostridium perfringens in Ready-to-eat Jokbal (Pig's Trotters)

Ready-to-eat (RTE) Jokbal (Pigs trotter), which consists of pigs feet cooked in soy sauce and various spices, is a very popular and widely sold in Korean retail markets. Commercially, the anaerobically packed Jokbal have also become a popular RTE food in several convenience stores. This study evaluates the effects of storage temperature and packaging methods for the growth of C. perfringens in Jokbal. Growth kinetic parameters of C. perfringens in aerobically and anaerobically packed Jokbals are determined at each temperature by the modified Gompertz equation. The lag time, specific growth rate, and maximum population density of C. perfringens are being analyzed as a function of temperature and packaging method. The minimum growth temperature of C. perfringens in aerobically and anaerobically packed Jokbal is 24℃ and 18℃, respectively. The C. perfringens in Jokbal did not grow under conditions of over 50℃ regardless of the packaging methods, indicating that the holding temperature of Jokbal in markets must be maintained at above 50℃ or below 18℃. Growth of C. perfringens in anaerobically packed Jokbal is faster than in aerobically packed Jokbal when stored under the same conditions. This indicates that there are a higher risks associated with C. perfringens for anaerobically packed meat products.