Hye-Jeong Yun

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

Comparison of sample preparation methods for the recovery of foodborne pathogens from fresh produce.

Sample preparation methods (pummeling, pulsifying, sonication, and shaking by hand) were compared for achieving maximum recovery of foodborne pathogens from iceberg lettuce, perilla leaves, cucumber, green pepper, and cherry tomato. Antimicrobial and dehydration effects also were examined to investigate causes of poor recovery of pathogens. Each produce type was inoculated with Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus at 6.0 log CFU/cm(2), and samples were prepared using the four methods. Bacterial populations recovered from the five types of produce were significantly different (P < 0.05) according to sample preparation methods and produce type. The bacterial populations recovered from pummeled and pulsified samples were higher (P < 0.05) than those recovered from sonicated and hand-shaken samples, except for cherry tomato. The number of bacteria recovered from produce was reduced (P < 0.05) from that of the inoculum by 0.16 to 2.69 log CFU/cm(2). Although extracts of iceberg lettuce, perilla leaves, cucumber, and green pepper had no antimicrobial activity, the populations of E. coli O157:H7, Salmonella Typhimurium, B. cereus, and L. monocytogenes in cherry tomato extract were slightly reduced after these treatments (P < 0.05). The pathogen populations on perilla leaves and cherry tomatoes decreased by >2 log CFU/cm(2) after exposure to 40% relative humidity for 1 h. No reduction was observed when the five pathogens were exposed to 90% relative humidity. These data suggest that pummeling and pulsifying are optimal sample preparation methods for detection of microorganisms. Acidic produce such as cherry tomato should be treated with a method that does not cause sample breakdown so that acid stress on the bacteria can be minimized. Dehydration stress also affects recovery of pathogens from produce.

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.

Analyses of Microbiological Contamination in Cultivation and Distrubution Stage of Tomato and Evaluation of Microbial Growth in Tomato Extract

This study investigated the microbiological contamination of tomato in cultivation and distribution stage. Growth of Escherichia coli O157:H7 and Listeria monocytogens examined in tomato extracts (0.1, 1.0, and 10.0%) and incubation temperatures (5, 15, 25, and 35 o C). In cultivation stage of tomato, total aerobic bacteria were 7.77 log CFU/g in gloves of APC (Agricultural Products Processing Center) worker and Bacillus cereus were 0.33 log CFU/g at nutrient tank, respectively. And Staphylococcus aureus, Salmonella spp., were not detected. After APC stage, total aerobic bacteria were significantly higher compared with before-APC stage. Among of general, pes- ticide-free and organic produce in tomato were no significant difference in microbial contamination. Coliforms of tomato in small vinyl package were significantly higher when compared to tomato in whole boxes package. There was no significant difference in bacteria count between unwashed tomato and washed tomato using tap water for one minute. The growth of E. coli O157:H7 and L. monocytogens in tomato extracts were decreased significantly as the concentration increased, and the microbial population was reached the lowest point during storage in 10% tomato extracts concentration for 72h at 5 o C. However, the population of E. coli O157:H7 and L. monocytogens were gradu- ally increased at 7.33~8.51 and 7.73~8.60 log CFU/ml during storage at 15~35 o C for 72h, respectively.

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.

Characteristics of Water Quality at Main Streams and Lake Doam in Daegwallyeong Area

This study was surveyed that water physiochemical characteristics and phytoplankton incidence of main stream and Lake Doam near to Daegwallyeong agricultural area. Based on above results, it was conducted to get information overall water characteristics in south Han upstream river. COD value of Lake Doam was and T-P (Total phosphorous) from there was which was higher than the value of grade VI based on lake water living environment standard. Suspended solid was an average of 9.77 NTU which was higher than value of lake living standard. Concentration of phytoplankton was over from July to September. It was considered that cyanobacteria were occurred due to massive influx of nutrient material by high temperature and rainfall during this season. Compare to Ontarios sediment quality guidelines, T-N and T-P was middle value between LEL and SEL in Lake Doam. This value means that contamination in water is serious. Therefore, it is considered that systematic management was needed to reduce and block contamination source.

Gray Mold on Carrot Caused by Botrytis cinerea in Korea

Gray mold caused by Botrytis cinerea was found on a carrot seedling in a greenhouse and a field at Daegwallryeong, Gangwon Province in 2007-2009. Symptoms included irregular, brown, blight, or chlorotic halo on leaves and petioles of the carrots. Fungal conidia were globose to subglobose or ellipsoid, hyaline or pale brown, nonseptate, one celled, () in size, and were formed on botryose heads. B. cinerea colonies were hyaline on PDA, and then turned gray and later changed dark gray or brown when spores appeared. The fungal growth stopped at , temperature range for proper growth was on MEA and PDA. Carrots inoculated with ml conidial suspension were incubated in a moist chamber at for pathogenicity testing. Symptoms included irregular, brown, water-soaked rot on carrot roots and irregular, pale brown or dark brown, water-soaked rot on leaves. Symptoms were similar to the original symptoms under natural conditions. The pathogen was reisolated from diseased leaves, sliced roots, and whole roots after inoculation. As a result, this is the first report of carrot gray mold caused by B. cinerea in Korea.