Dong-Sul Kim

Effect of Gamma Irradiation on the Survival of Pathogens in Kwamegi, a Traditional Korean Semidried Seafood

Kwamegi (semidried raw Pacific saury) is traditional seafood available in Korea. It has water activity in the range of 0.90 to 0.95. Spoilage and the growth of most pathogenic bacteria is retarded because of low water activity, low temperature, and packaging. However, it is contaminated with bacteria of public health significance and poses a hazard to the consumer because it is consumed raw without any cooking. The effectiveness of these hurdles in preventing the growth of Staphylococcus aureus, Bacillus cereus, Salmonella Typhimurium, and Escherichia coli and the efficacy of irradiation treatment in eliminating these bacteria from kwamegi using inoculated pack studies was examined. Radiation sensitivity of S. aureus, B. cereus, Salmonella Typhimurium, and E. coli in kwamegi was investigated. D10-values of these organisms in kwamegi were 590 +/- 13.6, 640 +/- 14.9, 560 +/- 45.4, and 550 +/- 8.6 Gy, respectively. The growth of all four test organisms inoculated into these foods during 4 weeks of storage at an ambient winter temperature (ranging from -5 degrees C to +5 degrees C) was recorded. All four pathogens (inoculated at 10(6) CFU/g) were eliminated by irradiation at 4 kGy. These studies unequivocally demonstrate that irradiation, with a combination of low water activity and low temperature, results in microbiologically safe kwamegi.

Fumonisins B1 and B2 in Agricultural Products Consumed in South Korea : An Exposure Assessment

To survey fumonisins B1 (FB1) and B2 (FB2) in agricultural products consumed in South Korea and provide an exposure assessment, ground samples were extracted (80% MeOH), filtered (0.2 microm), and cleaned up. After evaporation, dry residues were reconstituted in 50% MeOH, and a 50-micro1 aliquot of this sample was mixed with 200 micro1 of o-phthaldialdehyde for derivatization. The derivatives were analyzed with a high-performance liquid chromatography system equipped with a fluorescence detector. For validation of the detection procedure, linearity, accuracy, precision, detection limit, and quantification limit were determined. The validated detection method was then used to survey fumonisins in white rice, brown rice, barley, barley tea, beer, wheat flour, millet, dried corn, corn flour, corn tea, canned corn, popcorn, and breakfast cereal. Retention times for FB1 and FB2 standards were 7 and 18 min, respectively. Linearity (R2 = 0.99995 to 0.99998), accuracy (81.47 to 108.83%), precision (2.35 to 5.77), detection limit (25 ng/g or ng/ml), and quantification limit (37 ng/g or ng/ml) indicated that this procedure is capable of quantifying fumonisins in agricultural products. Only FB1-positive samples (5.12%, three dried corn samples and five corn flour samples) were found at 90.89 to 439.67 ng/g. According the survey results, an estimated daily intake of FB1 and FB2 in Korea was 0.087 ng/kg of body weight per day. These results indicate that continuous monitoring of these mycotoxins is necessary to establish appropriate risk assessment, and the maximum tolerable daily intake of fumonisins in Korea is lower than the 2 microg/kg set by the Joint Food and Agriculture Organization-World Health Organization Expert Committee.