• Preventive Nutrition and Food Science
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• v.9 no.3
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• pp.236-239
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• 2004

Microbial contamination of ready-to-eat ingredients for Kimbab manufacturing and the effect of irradiation to reduce the microbial contamination of the products were investigated. Among 9 food items tested, there were no viable cells in the ham, seasoned and cooked beef, imitation crab leg, fried egg, and seasoned burdoc. Cucumber, surimi gel, and seasoned and blanched spinach were counted at 5.07$\pm$0.97, 3.50$\pm$0.14, and 5.41$\pm$0.51 log CFU/g, respectively. Irradiation at 1 kGy reduced the number of microorganism in these ready-to-eat foods to an undetectable level. However, the dried laver showed an 8.83$\pm$0.10 log CFU/g and an irradiation at 3 kGy reduced the level to only 7.14$\pm$0.23. Sensory evaluation of the irradiated Kimbab prepared from these food materials indicated that the measure of the control of the sensorial quality should be provided before applying an irradiation to the prepared Kimbab.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.6
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• pp.1116-1121
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• 1997

Effects of gamma irradiation onf the activity and the properties(amino acid compositions, in vitro digestibility and SDS-PAGE pattern) of proteolytic enzymes were investigated. The proteolytic activity of soluble human serine protease, enzyme in kiwi and pineapple decreased 10% and 30~65% by 5 kGy and 30 kGy, respectively. In dried pancreatin and lysozyme, the proteolytic and antimicrobial activities decreased 6~14% and 10~20% by 5kGy and 40kGy, respectively. The analysis of above 10kGy-irradiated soluble human serine protease by SDS-PAGE revealed radiolysis of the enzyme into protein or peptides of lower molecular weights. The irradiation of skim milk, hammastein casein, and lysozyme up to 40kGy had no deleterious effect on either the in vitro digestibility or amino acid compositions.

• Food Science and Biotechnology
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• v.17 no.4
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• pp.861-864
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• 2008

Enterobacter sakazakii, Salmonella typhimurium. and Bacillus cereus were evaluated on inoculated infant formula by gamma irradiation treatment as a method to provide microbial safety. The infant formula inoculated with the major pathogenic bacteria was treated at irradiation dose of 0, 3, 5, and 10 kGy, respectively. After treatment, the samples were individually packaged and stored at $20^{\circ}C$. Microbiological data during storage represented that the populations of E. sakazakii, S. typhimurium, and B. cereus were reduced with the increase of irradiation dose by 4 to 5 log reductions. In particular, E. sakazakii, S. typhimurium. and B. cereus were eliminated at 10, 5, and 3 kGy, respectively. E. sakazakii was the most radiation-resistant, while B. cereus was the least. Our results represent that gamma irradiation below 10 kGy should eliminate the growth of the major pathogenic bacteria in infant formula during storage.

• Preventive Nutrition and Food Science
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• v.11 no.4
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• pp.344-347
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• 2006

This study evaluated the use of electron beam irradiation for decontamination of the Korean medicinal herb, Angelica gigas Nakai. Herb samples were irradiated at doses of 2, 8, and 16 kGy, respectively. Populations of microorganisms in Angelica gigas Nakai decreased by 2$\sim$3 log cycles at 8 kGy irradiation. Electron beam irradiation caused negligible changes in Hunter color L, a, and b values. Sensory evaluations of Angelica gigas Nakai confirmed that irradiation caused no significant changes in the organoleptic properties of the samples. These results suggest that electron beam-irradiated herbs retain a better microbial safety and sensory qualities, compared with the non-irradiated.

• Korean Journal of Food Science and Technology
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• v.30 no.5
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• pp.1184-1188
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• 1998

Effects of gamma irradiation on pigments of beef was investigated by determination of the Hunter's color values and pigments such as myoglobin, metmyoglobin and oxymyoglobin after gamma irradiation up to 5 kGy in air or vacuum package for 7 days. 'L' and 'b' values increased but 'a' value decreased with the elapse of the storage period. But, 'L', 'a' and 'b' values of irradiated beef were lower than non-irradiated beef. Myoglobin decreased but oxymyoglobin and metmyoglobin increased with the elapse of the storage period. Myoglobin decreased but oxymyoglobin and metmyoglobin increased with gamma irradiation up to 5 kGy. In regard to packaging methods, vacuum package did not affect pigment of the beef as did air package.

• Journal of Microbiology and Biotechnology
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• v.33 no.1
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• pp.106-113
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• 2023

The supply of microbiological risk-free water is essential to keep food safety and public hygiene. And removal, inactivation, and destruction of microorganisms in drinking water are key for ensuring safety in the food industry. Ultraviolet-C (UV-C) irradiation is an attractive method for efficient disinfection of water without generating toxicity and adversely affecting human health. In this study, the disinfection efficiencies of UV-C irradiation on Shigella flexneri (Gram negative) and Listeria monocytogenes (Gram positive) at various concentrations in drinking water were evaluated using a water purifier. Their morphological and physiological characteristics after UV-C irradiation were observed using fluorescence microscopy and flow cytometry combined with live/dead staining. UV-C irradiation (254 nm wavelength, irradiation dose: 40 mJ/cm²) at a water flow velocity of 3.4 L/min showed disinfection ability on both bacteria up to 10⁸ CFU/4 L. And flow cytometric analysis showed different physiological shift between S. flexneri and L. monocytogenes after UV-C irradiation, but no significant shift of morphology in both bacteria. In addition, each bacterium revealed different characteristics with time-course observation after UV-C irradiation: L. monocytogenes dramatically changed its physiological feature and seemed to reach maximum damage at 4 h and then recovered, whereas S. flexneri seemed to gradually die over time. This study revealed that UV-C irradiation of water purifiers is effective in disinfecting microbial contaminants in drinking water and provides basic information on bacterial features/responses after UV-C irradiation.

• Korean Journal of Food Science and Technology
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• v.31 no.4
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• pp.1005-1010
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• 1999

To study the shortening of rigor mortis and changes in the morphological properties of gamma-irradiated pre-rigor bovine muscle (M). Sternomandibularis during post mortem, this experiment was performed with a test of shear force and the observation of the ultrastucture of raw muscle. The time elapsed until maximum shear force values was shortened by gamma irradiation, depending upon the dose. The release of rigor mortis started earlier than control (non-irradiated muscle). A shortening of the length of the Z-line and the maintenance of the sarcomere length by gamma irradiation was observed. The breakdown of the perimysium of muscle bundles was observed more in irradiated samples than in the control. In conclusion, it is considered that gamma irradiation on pre-rigor beef shortens aging-period, improves tenderness and enhances the beef quality.

• Proceedings of the Korean Society of Food Hygiene and Safety Conference
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• 1994.03a
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• pp.1-11
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• 1994

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2003.10a
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• pp.135.1-135
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• 2003

To elucidate the effect of gamma-irradiation on the molecular properties of hemoglobin, the secondary, tertiary structure, and the molecular weight size of the protein were examined after irradiation at 0.5, 1, 5, and 10 kGy. Gamma-irradiation of hemoglobin solutions caused the disruption of the ordered structure of the protein molecules, as well as degradation, cross-linking, and aggregation of the polypeptide chains. A SDS-PAGE study indicated that irradiation caused initial fragmentation of the proteins and subsequent aggregation due to cross-linking of the protein molecules. The effect of irradiation on the protein was more significant at lower protein concentrations. Ascorbic acid decreased the degradation and aggregation of proteins by scavenging oxygen radicals that were produced by irradiation. A circular dichroism study showed that irradiation decreased the helical content of hemoglobin with a concurrent increase of the aperiodic structure content. Fluorescence spectroscopy indicated that irradiation decreased the emission intensity that was excited at 280 nm.

• Journal of Microbiology and Biotechnology
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• v.12 no.6
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• pp.1010-1012
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• 2002

In order to isolate carotenoid-hyperproducing yeast, low-dose gamma irradiation was used as means of mutagenesis. Phaffia rhodozyma was treated by gamma irradiation of less than 10 kGy, which is considered to be a wholesome irradiation condition established by the Food and Drug Administration. Through repeated rounds of gamma irradiation and visual screening, mutant 3A4-8 was obtained. It produced a $3,824{\mu}g$ carotenoid/g yeast, 69% higher content than $2,265{\mu}g/g$ yeast of the unirradiated one. This result indicates that low-dose gamma irradiation could be used as means of mutagenesis to obtain carotenoid-hyperproducing strain of Phaffia rhodozyma, since only carotenoid-hyperproducing yeast survived gamma irradiation by scavenging oxygen radicals generated by radiolysis of water.