• Journal of Food Hygiene and Safety
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• v.28 no.2
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• pp.168-173
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• 2013

This study was carried out to develop and validate predictive models of E. coli O157:H7 growth. Growth data of E. coli O157:H7 in Paprika were collected at 12, 24, 30 and $36^{\circ}C$. The population increased into 3.0 to 3.8 log10 CFU/g within 4 days, then continued to increase at a slower rate through 10 days of storage at $12^{\circ}C$. The lag time (LT) and maximum specific growth rate (SGR) obtained from each primary model was then modeled as a function of temperature using Davey and square root equations, respectively. For interpolation of performance evaluation, growth data for a mixture of E. coli O157:H7 were collected at time intervals in paprika incubated at the different temperatures, which was not used in model development. Results of model performance for interpolation data demonstrated that induced secondary models showed acceptable goodness of fit. Relative errors in the LT and SGR model for interpolation data (18 and $27^{\circ}C$) was 100%, which show acceptable goodness of fit and validated for interpolation. The primary and secondary models developed in this study can be used to establish tertiary models to quantify the effects of temperature on the growth of E. coli O157:H7 in paprika.

• Journal of Bio-Environment Control
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• v.19 no.4
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• pp.343-350
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• 2010

This study was conducted to investigate the effect of harvest seasons on quality and microbial population at different steps of production chain of fresh-cut iceberg lettuce. Iceberg lettuces harvested in May, June, July, October, and December were processed following industrial practices, and stored at $5^{\circ}C$ for 9 days. For microbial measurement, samples were taken from each of the following steps: harvest, transport, pretreatment, cutting, 1st-washing, 2nd-washing, and day 3, 6, and 9 of storage. Iceberg lettuce cultivated in protect house and harvested in May and October showed higher $CO_2$ levels in the packages and electrolyte leakages than lettuce harvested in June, July and December. Microbial population of raw materials harvested in July was highest (6.76 log), and microbial growth rate during storage was highest in samples harvested in May. Lettuce harvested in June had better quality and microbial safety compared to other lettuces. Although lettuce harvested in October and December had less microbial population in either raw materials or processed products, those samples had inferior quality due to off-odor development and severe browning. Therefore, it is required to maintain quality and ensure microbial safety to distribute fresh-cut lettuce with high quality and safety throughout the year.

• Journal of Food Hygiene and Safety
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• v.18 no.4
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• pp.237-242
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• 2003

Sequences of industrial microbial counts of foods shows irregular fluctuating patterns as adeinition of fluctuating microbial counts(FMC). Recently, it beame clear that the FMC was considered as having a lognormal distribution as a first order approximation. Application of lognormal distribution to the industrial microbial counts could produce useful information in practice. This study is intended to verift the application method of lognormal idstribution in FMC. The one year's records for microbial counts of frozen dumplings from two companies were obtained, and the statistical analysis was carried out to estimate the frequencies of future events where counts exceeding selected levels and to compare the sanitation level of the two companies. The results showed that this spplication method enable translation of irregular recourds of microbial counts into an useful information such as te actual probalities of outburst of a given level and the quantitative predictions of potential hazards in the processing.

• Research in Plant Disease
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• v.17 no.1
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• pp.38-43
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• 2011

Almost 10~30% of vegetables were discarded by the spoilage from farms to tables. After harvest, vegetables are often spoiled by a wide variety of microorganisms including many bacterial and fungal species. This investigation was conducted to extent the knowledge of relationship the spoilage of vegetables and the diversity of microbes. The total aerobic bacterial numbers in fresh lettuce, perilla leaf, and chicory were $2.6{\sim}2.7{\times}10^6$, $4.6{\times}10^5$, $1.2{\times}10^6\;CFU/g$ of fresh weight, respectively. The most common bacterial species were Pseudomonas spp., Alysiella spp., and Burkholderia spp., and other 18 more genera were involved in. After one week of incubation of those vegetables at $28^{\circ}C$, the microbial diversity had been changed. The total aerobic bacterial numbers increased to $1.1{\sim}4.6{\times}10^8$, $4.9{\times}10^7$, and $7.6{\times}10^8\;CFU/g$ of fresh weight for lettuce, perilla leaf, and chicory that is about $10^2$ times increased bacterial numbers than that before spoilage. However, the diversity of microbes isolated had been simplified and fewer bacterial species had been isolated. The most bacterial population (~48%) was taken up by Pseudomonas spp., and followed by Arthrobacter spp. and Bacillus spp. The spoilage activity of individual bacterial isolates had been tested using axenic lettuce plants. Among tested isolates, Pseudomonas fluorescence and Pantoea agglomerans caused severe spoilage on lettuce.

• Journal of Food Hygiene and Safety
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• v.31 no.6
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• pp.451-457
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• 2016

The purpose of this study was to determine the antimicrobial effects of $ClO_2$ gas on pathogenic E. coli and Salmonella spp. colonizing on the fruit surface of strawberries for export. Factorial design was employed to treat strawberries inoculated with pathogenic E. coli or Salmonella spp. with a combination of $ClO_2$ gas concentrations (10, 20, 30, 40, and 50 ppmv), RH (50, 70, and 90%), and treatment time (0, 5, 10, 20, and 30 min). Interaction between the factors was observed to note that the reduced levels of microbial population were the highest when RH is set at 90% with gas concentration- and treatment time-dependent manner. With RH and gas concentration fixed at 90% and 50 ppmv, the populations of E. coli and Salmonella spp. decreased by 2.07 and 2.28 log CFU/g when treated for 20 min whereas population reduction by 0.5 and 0.7 log CFU/g were observed when treated for 5 min, respectively. The results help establish most effective conditions for $ClO_2$ gas treatment to enhance microbial safety of strawberries for export.

• Journal of The Korean Society of Integrative Medicine
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• v.4 no.4
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• pp.109-117
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• 2016

Purpose : This study was designed to provide basic data of effective sanitization method of sprout vegetable for microbiological safety. Methods : Sanitization treatments were performed by dipping the sprout into chlorine and vinegar water. Microbial analysis were composed of the total plate count(TPC) and coliform group count(CGC). Result : Among chlorine water sanitization, the microbial reduction was largest in 100ppm chlorine water, and its TPC and coliform group count decreased to 6.01 log CFU/g and 5.06 log CFU/g. The effective dipping time in 100ppm chlorine water treatment was 5.97 log CFU/g and 5.91 log CFU/g for 30min and 60min, in which TPC were below the microbiological safety limits of 6.00 log CFU/g. Coliform group counts were decreased to 5.44, 5.46, 5.42 log CFU/g in the dipping the spouts for 30min, 60min and 90min. As a result of sanitizing alfalfa spout by vinegar water, a microbial counts tended to decrease with increasing concentration and the dipping time. The effective concentration of vinegar water was 2% for TPC(6.00 log CFU/g) and 1% for coliform group count(5.20 log CFU/g). With 1% vinegar water treatment, TPC became below the microbiological safety limits in all samples and in particular, the sample treated for 60min and 90min(4.93, 4.54 log CFU/g). While coliform group counts were decreased to 3.91 log CFU/g in the dipping the sprouts for 90min, those were still beyond the permitted limit. Conclusion : To secure the food safety of food service facilities including kindergarten feeding, it is considered that along with the systematic study of effective disinfection method for microbiological control at the preconditioning level of spout vegetable within the range of secured maleficence to human body, and the study regarding the measures to lower the initial microbiological pollution of spout vegetable.

• The Korean Journal of Mycology
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• v.46 no.4
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• pp.459-466
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• 2018

In January 2017, discolored black oat seeds were found in the storage depot of a farmhouse in Jeongeup. Pyrenophora sp. was detected in 45% of the oat seeds surveyed. All Pyrenophora isolates obtained from the seeds were identified as Pyrenophora avenae based on the sequences of internal transcribed spacer (ITS) rDNA regions and glyceraldehyde 3-phosphate dehydrogenase (GPDH) gene and validated by morphological and cultural characterization. A phylogenetic tree constructed using the ITS and GPDH sequences showed that the Korean isolates of P. avenae comprise of four genetically distinct groups. Pathogenicity test validated that the fungus is an infectious agent responsible for discolored black seeds and leaf blotch in oat plants. This is the first study report that P. avenae causes leaf blotch disease of oat in Korea.

• Journal of Food Hygiene and Safety
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• v.29 no.4
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• pp.253-259
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• 2014

This study was conducted to investigate survival of Bacillus cereus (B. cereus) on stainless steel and polyvinyl chloride (PVC) and its transfer from two material to lettuce. The stainless steel and PVC were innoculated with B. cereus and stored at 6 combination conditions (temperature : $20^{\circ}C$ and $30^{\circ}C$, relative humidity (RH) : 43%, 69%, and 100%). Although the total numbers of B. cereus at RH 43% and RH 69% were reduced by 3.53-4.00 log CFU/coupon within 24 h regardless of material type, the spore numbers of B. cereus was lasted at 3.0 log CFU/coupon. When two materials were stored at $30^{\circ}C$, RH 100%, the spore numbers of B. cereus was rapidly increased by 3.0 log CFU/coupon. In addition, the reduction rate of B. cereus was decreased in the presence of organic matter. Transfer rate of B. cereus from surface of stainless steel and PVC to lettuce was increased by 10 times in the presence of water on the lettuce surface. As a result of this study, the presence of B. cereus on produce contact surfaces can increase the risk of cross-contamination. Thus, it is important that the packing table and conveyer belt in post harvest facility should be properly washed and sanitized after working to prevent cross-contamination.

• Research in Plant Disease
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• v.17 no.3
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• pp.272-279
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• 2011

Fusarium species are worldwide causal agents of Fusarium head blight (FHB) in cereals such as barley and wheat. Their toxigenic potential is a health risk for both humans and animals. To survey the natural occurrence of FHB and mycotoxins produced by Fusarium, total 126 barley or wheat grains grown in 2009-2010 season in Korea were collected. The incidence of FHB was 30.7% in silage barley, 26.9% in wheat, 20.7% in naked barley, 19.4% in malting barley, 16.4% in unhulled barley. Overall FHB incidence of barley and wheat in 2010 was 23.0% and 10% higher than that of 2009. The incidences and level of deoxynivalenol (DON), nivalenol (NIV), and zearalenone (ZEA) were 34%, 0.89 mg/kg, 84.9%, 1.86 mg/kg, and 10.3%, 0.06 mg/kg respectively. The both levels and incidences of NIV were found to be highest in barley, whereas the level of DON was found to be highest in wheat. Incidences of DON and NIV and the level of NIV in the samples from southern regions of Korea were higher than those from central region, whereas the level of DON from central region was higher than that from southern regions. This is the first paper demonstrating regional difference in natural occurrence of DON and NIV in wheat and barley.

• The Korean Journal of Mycology
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• v.50 no.4
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• pp.281-289
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• 2022

Fusarium head blight is an important disease of small grains. It is mainly caused by members of the Fusarium graminearum species complex (FGSC). Barley and wheat growers spray fungicides, especially demethylation-inhibitor fungicides, to suppress the disease. The objective of this study was to examine the changes in the sensitivity of the FGSC population to the triazole fungicide, propiconazole. A total of 124 and 350 isolates of FGSC were obtained from barley and wheat in Jeolla Province during 2010-2016 and 2020-2021, respectively. The species identity and trichothecene chemotypes of the FGSC isolates were determined based on polymerase chain reaction assays targeting translation elongation factor 1-alpha and TRI12 genes, respectively. Sensitivity to propiconazole was determined based on the effective concentration that reduced 50% of the mycelial growth (EC₅₀) using the agar dilution method. Of all isolates, F. asiaticum with the nivalenol chemotype was the most common (83.9% in 2010-2016 and 96.0% in 2020-2021), followed by F. asiaticum with the 3-acetyl deoxynivalenol chemotype (12.1% in 2010-2016 and 2.9% in 2020-2021). The EC₅₀ values of the isolates collected in 2010-2016 and 2020-2021 ranged from 0.0180 to 11.0166 ㎍/mL and 1.3104 to 17.9587 ㎍/mL, respectively. The mean EC₅₀ value of the isolates increased from 3.8648 ㎍/mL in 2010-2016 to 5.9635 ㎍/mL in 2020-2021. The baseline resistance to propiconazole was determined to be 7 ㎍/mL, based on the EC₅₀ value of isolates collected in 2010-2016, and the ratio of resistant isolates increased from 9.7% in 2010-2016 to 28.6% in 2020-2021.