Kyoung-Yul Ryu

Distribution of Microorganisms in Perilla Leaf and Cultivation Area

The prevalence and distribution of hazardous microorganisms were investigated from the major perilla cultivation area at Milyang, Gyeongnam province, Korea. Aerobic plate count (APC) and coliform count of perilla leaves were 4.82 log CFU/g and 3.85 log CFU/g, respectively. E. coli, S. aureus and B. cereus were detected in 3.0% (4/114), 7.9% (9/114) and 46.5% (53/114) of examined perilla leaves. However, E. coli O157:H7, Salmonella spp, and L. monocytogenes were not detected. The distribution of hazardous microorganisms in perilla leaf cultivation environment were compared and the concentration of APC and coliform counts were more than 3.0 log CFU/(mL, g, 100 cm 2 , hand) from most of the samples. S. aureus were detected from irrigation water, packing table, packing vinyl, hand, and clothes. Also, B. cereus was frequently detected from the examined samples. Especially, packing table and collection container were contaminated with maximum 5.5 log CFU/100 cm 2 of B. cereus. Good Agricultural Practice (GAP) system should be

Biological Hazard Analysis of Angelica gigas Nakai on Production and Marketing Steps

This study is aimed to investigate microbiological contamination of Angelica gigas Nakai. A total of 111 samples including root, soil, and irrigation water were collected from farms and market to detect aerobic bacteria, Bacillus cereus, coliform, Escherichia coli, Listeria monocytogenes,. Salmonella spp., and Staphylococcus aureus. The contaminations of aerobic bacteria, coliform, and Bacillus cereus in the root during cultivation were found 6.71 log CFU , 4.13 log CFU , and 3.54 log CFU , respectively. The contamination of coliform and B. cereus were detected in all steps from harvesting to processing, with the highest count recorded from the cutting step. In marketing, the contaminations of aerobic bacterial, coliform, and B. cereus were 5.5~6.0 log CFU , 2.4~2.6 log CFU , and 3.5~4.0 log CFU , respectively. Listeria monocytogenes, Salmonella spp, and Staphylococcus aureus were not detected in any of samples. This result indicated that hygienic soil management and post harvest management should be performed to reduce the contamination of hazard microorganisms and to produce safe agro-products.

Investigation of Microbial Contamination Levels of Leafy Greens and Its Distributing Conditions at Different Time - Focused on Perilla leaf and Lettuce -

The objective of this study was to investigate and evaluate microbial contamination levels of leafy greens (perilla leaf and lettuce) and its distributing conditions at different seasons (Feb, May, Aug, and Nov of the year 2011) in order to provide insight into any potential health hazards associated with consumption of these commodities. Leafy greens were collected from a farm located in Geumsan, Chungnam and wholesale markets (WM) and traditional markets (TM) located in Suwon. At the same time, temperature and relative humidity fluctuations experienced by the leafy greens during distribution from the farm to the distribution center were measured by a data logger. The contam- ination levels of perilla leaf and lettuce were determined by analyzing total plate count. Coliform groups, Bacillus cereus, Escherichia coli, Escherichia coli O157:H7, Salmonella spp., Listeria monocytogenes and Staphylococcus aureus were determined. The contamination levels of total aerobic bacteria, coliform groups and B. cereus in both vegetables sampled during May and August found to be higher than those sampled during February and November. E. coli O157:H7, Salmonella spp., L. monocytogenes were not detected in the vegetables analyzed in this study. There were no significant trends between samples at WM and TM in the contamination levels. Relative humidity of vegeta- bles distributed from the farm to the distribution center showed over 90% during distribution regardless of measured seasons. In the case of background microflora on leafy greens, the density was significantly increased at 20, 30 and 37 o C during storage of 24h. E. coli O157:H7 and B. cereus inoculated on the leaves also showed similar increases in the storage tests. The microbial contamination levels determined in this study may be used as the fundamental data for microbial risk assessment.

Profiles of Toxin Genes and Antibiotic Susceptibility of Bacillus cereus Isolated from Perilla Leaf and Cultivation Areas

Two-hundred Bacillus cereus isolated from perilla leaf cultivation areas in Miryang, Korea were investigated for toxin genes and antibiotic susceptibility. Toxigenic patterns of isolates were identified to be 11 groups through toxin gene profiles. 21% of strains isolated from the perilla leaves had both enterotoxin and emetic toxin. Toxin genes entFM (100%), nheA (100%) and hblA, C, D (65.5%) were frequently found in the perilla leaves, whereas EM (21.0%) was less common. Most isolates were susceptible to 10 antibiotics, but they were highly resistant to penicillin (100%), ampicillin (100%), oxacillin (94.9%), amoxicillin-clavulanic acid (95.6%), cefazolin (78.2%), and rifampicin (58.0%). These results indicate that food-borne outbreak caused by B. cereus might lead to diarrhea and emetic syndromes.

Evaluation of Resistance to Ralstonia solanacearum in Tomato Genetic Resources at Seedling Stage

Bacterial wilt of tomatoes caused by Ralstonia solanacearum is a devastating disease that limits the production of tomato in Korea. The best way to control this disease is using genetically resistant tomato plant. The resistance degree to R. solanacearum was evaluated for 285 tomato accessions conserved in the National Agrobiodiversity Center of Rural Development Administration. These accessions of tomato were originated from 23 countries. Disease severity of tomato accessions was investigated from 7 days to 14 days at an interval of 7 days after inoculation of R. solanacearum under greenhouse conditions. A total of 279 accessions of tomato germplasm were susceptible to R. solanacearum, resulting in wilt and death in 70 to 90% of these plants. Two tomato accessions were moderately resistant to R. solanacearum. Only four accessions showed high resistance against R. solanacearum. No distinct symptom of bacterial wilt appeared on the resistant tomato germplasms for up to 14 days after inoculation of R. solanacearum. Microscopy of resistant tomato stems infected with R. solanacearum revealed limited bacterial spread with thickening of pit membrane and gum production. Therefore, these four resistant tomato germplasms could be used in tomato breeding program against bacterial wilt.

Effects of LED Treatment on Microbial Reduction and Quality Characteristics of Red Pepper Powder

This study investigated reduction of microbial population, water soluble pigment, capsanthin con- tent, surface color (Hunter L, a, b, ∆E), and sensory properties of pepper powder by LED (red, yellow, blue, green) treatments. LED (red, yellow, blue, green) treatment were conducted in 1,000 lux storage at 25 o C for 10 days. The total aerobic bacteria was no significant difference among the control and treated with LED during 10 days. In yellow LED treatment, yeast and molds were decreased about 1.76 log. Surface color such as lightness (L), redness (a), yel- lowness (b) were showed a decreasing tendency as the storage period. In the overall color difference (∆E) of yellow LED treatment was lower less than 3.0. Water soluble pigment was no difference in control and LED treated samples during storage period. Capsanthin content was significantly decreased as storage period was increased, but no signif- icant differences were observed among red and yellow LED treatments. Sensory properties of control was signifi- cantly reduced by storage period but yellow and green LED treatments were no significantly differences.

Evaluation of Selective Media for Isolation of Staphylococcus aureus from Agricultural Products

Five kinds of selective media, such as mannitol salt agar (MSA), Baird-Parker agar (BPA), Baird- Parker supplemented with rabbit plasma fibrinogen (BPA+RPF), CHROMagar Staphylococcus aureus (CSA), and Petrifilm Staph Express count system (Petrifilm), were compared to recommend the optimum selective media for iso- lation of Staphylococcus aureus from agricultural products. Seventy four target and non target bacteria were inocu- lated on five selective media to analyze sensitivity and specificity. In the recovery test of injured S. aureus cells, S. aureus was exposed to acid (1% lactic acid for 10 min), heat (60 o C for 90s), and cold (�20 o C for 1h) conditions. And artificially contaminated agricultural products (iceberg lettuce, green pepper, and cherry tomato) was enumerated on five selective media. The sensitivity of BPA+RPF, CSA, Petrifilm, MSA, and BPA were 100%, 100%, 100%, 90.5%, 90.5%, respectively. In addition, the specificity of BPA+RPF, CSA, MSA, BPA and Petrifilm were 100%, 100%, 84.6%, 75.0%, 67.3%, respectively. However, no difference among five selective media was observed in recovery on injured S. aureus cell and enumeration from agricultural products. This results suggest that BPA+RPF and CSA are the optimum media for detection of S. aureus from agricultural products.

The Monitoring of Agricultural Environment in Daegwallyeong Area

In order to provide the basic information on the agricultural environment in Daegwallyeong Highland, the characters of weather, water, and soil quality were investigated. The meteorological characteristics was monitored by automatic weather system (AWS) at 17 sites. The quality of water for samples were collected monthly at 24 sites depending on landuse style. Soil samples were collected from a forest, grassland, and the major vegetable cultivation areas such as potato, carrot, Chinese cabbage, onion, head lettuce, and welsh onion field. The weather showed the mountain climate, and the average yearly temperature is 6.4℃, the average temperature in January is -7.6℃ and the average temperature in July is 19.1℃, and the change of temperature on the districts of Daegwallyeong is severe. The yearly record of precipitation shows 1717.2 mm. The water quality of crop field was worse than forest or grassland in Daewallyeong highland. In 2005, annual T-N, T-P, SS distribution of Chinese cabbage field showed 7.4~11.3, 0.061~0.1, and 3.0~53.0 mg L -1 . The potato field showed 3.1~7.2 , 0.019~0.056 and 0.5~3.0 mg L -1 , respectively. Being compared of water quality between potato field and chinese cabbage field, it showed that the water quality of Chinese cabbage field was worse than potato field. On farming, the soil of crop cultivation showed pH 5.6 to 6.8, 18.0~42.4 g kg -1 of OM, 316~658 mg kg -1 of Avail. P2O5. The content of cations showed 0.41~0.88 cmolc kg -1 of Exch. K, 3.73~7.07 cmolc kg -1 of Exch. Ca and 1.17~1.90 cmolc kg -1 of Exch. Mg.

Effects of Improved Heat Treatment on Microbial Reduction and Germination in Sprout Vegetable Seeds

This study investigated the germination and reduction of microbial population in domestic (radish, Chinese cabbage, and vitamin) and imported (radish and red cabbage) sprout seeds by heat treatment (40, 50, 60, and 70 o C for 15 min or 30 min). The germination ratio (define the ratio) was 45-97% at 24 h after treatment <60 o C and was decreased at 70 o C. In domestic radish seed, total aerobic bacteria were decrease by approximately 1.71 log CFU/g after heat treatment at 70 o C for 30 min and viable coliforms were decreased to under the detection limit at temperatures over 60 o C. Decrease of total aerobic bacteria and coliforms in domestic Chinese cabbage seed was 1.23-1.34 and 2.77 log CFU/g, respectively, after heat treatment over 60 o C. In domestic vitamin seed, total aerobic bacteria were decreased by about 0.3 log CFU/g at 70 o C for 15 min. In imported radish seed, total aerobic bacteria were decreased 2.12-2.30 log CFU/g after heat treatment over 60 o C. Total aerobic bacteria in imported red cabbage seed were reduced by 0.66-0.84 log CFU/g after heat treatment over 40 o C and coliforms were undetectable. In case of Bacillus cereus, there was no significant difference by heat treatment in any sample. Staphylococcus aureus and Salmonella sp. were not detected at the detection limit in any tested seeds at any temperature.

First Report of Fusarium Wilt Caused by Fusarium proliferatum on Safflower

annual plant of the family Asteraceae. Safflower has been widely cultivated in Korea, India, China, Egypt, Southern Europe, North America, and Australia (Lee, 1980). Safflower seeds contain α-linoleic acid, which used as cooking oil and clinically for the treatment of cataclasis, osteoporosis and rheumatoid arthritis in Korea (Kang et al., 1999; Kim, 1992; Lee et al., 2002). In addition, its flower has been utilized for folk medicine as an analgesic, antithrombotic and antihypertensive crude drug, as well as natural dye and food colorants (Han, 1988). It has been reported that main pathogens on safflower are Alternaria alternata (leaf spot), Botrytis cinerea (gray mold), Colletotrichum acutatum (Anthracnose), Fusarium oxysporum (Fusarium wilt), Phytophthora cactorum (Phytophthora root rot), Puccinia carthami (rust), Sclerotium rolfsii (collar rot), and Sphaerotheca fuliginea (powdery mildew) worldwide (Farr and Rossman, 2016). Recently, we observed wilt symptoms on safflower grown in green house in Jeonju, Korea, thus leading to identify the causal agent of the wilt disease in this study.