• Korean Journal of Food Science and Technology
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• v.28 no.3
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• pp.587-592
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• 1996

Effects of high pressure on the inactivation and microstructure of Candida tropicalis (C. tropicalis) were in vestigated. High pressure inactivation of C. tropicalis was a first order reaction. The decimal reduction time (D value) at 400 MPa was 1.4 min at $25^{\circ}C$ and z value was 100 MPa. The effect of high pressure treatment was higher when treated at $45^{\circ}C$ than at $25^{\circ}C$. Damages in mitochondrial membrane and cell wall of C. Tropicalis were observed when it was pressurized at 400 MPa for 10 min. It indicates that high pressure affects the membrane system of the cell and causes the inactivation of C. tropicalis.

• Korean Journal of Food Science and Technology
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• v.22 no.7
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• pp.799-801
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• 1990

Of the several methods proposed for decreasing toxicity of Paralytic shellfish poison(PSP) from intoxicated shellfish, heat treatment has been most popular, although a large percentage of the incidents of PSP illness have been related to the ingestion of cooked shellfish. The purpose of this study was to determine the kinetics of PSP destruction at various temperatures. The homogenate of intoxicated blue mussel(Mytilus edulis) was heated at temperature ranging from $90\;to\;121^{\circ}C$ and toxicities measured in samples heated for various time intervals. The rate constant(k) per second was $3{\times}10^{-4},\;at\;90^{\circ}C,\;4.98{\times}10^{-4},\;at\;100^{\circ}C,\;7.38{\times}10^{-4},\;at\;116^{\circ}C,\;and\;8.38{\times}10^{-4},\;at\;121^{\circ}C,\;$. By the Arrhenius equation, the decimal reduction time(D-value) was $121min.\;at\;90^{\circ}C,\;82min,\;at\;100^{\circ}C,\;58min.\;at\;116^{\circ}C\;and\;53min.\;at\;121^{\circ}C$. The z-value, activation energy($E_a\;and\;Q_{10}$) was $72^{\circ}C,\;3.9{\times}10^7(J/kg\;mol)$ and 1.39, respectively.

• Korean Journal of Food Science and Technology
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• v.29 no.4
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• pp.710-715
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• 1997

Inactivation of lipoxygenase activity in Chinese cabbage was shown after salting and heat treatments. Crude lipoxygenase was obtained from treatment of $(NH_{4})_{2}SO_{4}$. Lipoxygenase activity in Chinese cabbage was about 50% after 20 hrs of salting in 13% (w/v) concentration. After heating at $90^{\circ}C$ for 15 min, residual activity of lipoxygenase was about 50%. Inactivation of lipoxygenase was highly accelerated by increasing temperature and heating time. Decimal reduction time (D-value) were 42, 20 and 14 min at 70, 80 and $90^{\circ}C$, respectively. When cabbage was soaked in 0.05 M $CaCl_{2}$ and heated at $55^{\circ}C$ for 1.5 hr, higher activity of crude lipoxygenase was found compared with the heat treatment without $CaCl_{2}$.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.2
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• pp.289-295
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• 2009

To develop a safer yogurt for immuno-compromised or allergy patients and to extend shelf-life, a plain yogurt was irradiated with doses of 0, 1, 3, 5, and 10 kGy using a gamma ray and the chemical and microbiological quality and allergenicity change were investigated. There was no difference in the content of protein, total solid, and amino acids of the plain yogurt by irradiation treatment and different storage temperatures (4, 20, and $35^{\circ}C$). The lactic acid bacterial counts of irradiated plain yogurt had approximately 3-decimal reduction at 3 kGy, and no viable cell at 10 kGy regardless of storage time and temperature. The binding ability of rabbit antiserum to milk proteins in irradiated plain yogurt showed that 10 kGy of irradiation produced significantly higher binding ability than other treatments. Sensory evaluation indicated that only appearance of the plain yogurt irradiated at 3 kGy or higher had a lower value than the non-irradiated control when stored at $20^{\circ}C$. Results suggest that irradiation of plain yogurt does not significantly affect the chemical and sensory quality of plain yogurt, but can extend the shelf-life, possibly reduce allergenicity, and provide a safer product.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.18 no.1
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• pp.42-63
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• 1992

In order to investigate the effect of nonionic surfactants on the antimicrobial activity of preservatives in the presence and absence of p.0.E(20) Sorbitan fatty acid ester commonly used in cosmetics and pharmaceutical systems, these experiments were carried out by determining Minimum Inhibitory Concentration(MIC) values and MIC values of adaptation against test organisms. And also the inactivation of the preservative against each microorganism in formula added with various concentrations of P.0.E(20) Sorbitan monostearate were measured by use of a preservative death time curve The results obtained were as fort low : 1) Nonionic surfactant inactivated Methylparaben to varying extents, but not Imidazolidinyl urea. 2) A combined preservative system was inactivated to a little extent (range of 0.16-0.20% Conc.), no adaptation was observed for the 5. aureus ATCC 6538. Imidazolidinyl urea complex combined with Methylparaben had a broad antibacterial spectrum against the Gram(.) and the Gram(-) bacteria It was found that preservatives had a synergistic effect by use of mixed form of preservatives, 3) In formula preserved with 0.2% Methylparaben containing 0.5, 1.0 and 2.0% P.0.E(20) Sorbitan monostearate, E. coli ATCC 10s36 and P. aeruginosa NCTC 10490 died quickly within in 2hr 4) However, from Fig.5, S. aereus ATCC 6538 died more slowly within increasing surfactant concentration and the D-values(Decimal reduction time) were 5.2, 8 and 14 hr. for samples containing 0.5, 1 0 and 2.0% P 0. E(20) Sorbitan monostearate, respectively. 5) In the case of Methylparaben, no adaptation for the E. coli ATCC 10536 6) All of the nonionic surfactant, p.0. E(20) Sorbitan fatty acid ester used in the experiments decreased the effectiveness of Methylparaben, but not of Imidazolidinyl urea.

• Korean Journal of Food Science and Technology
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• v.30 no.6
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• pp.1362-1366
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• 1998

The sterilizing effect of electron beam was compared with that of gamma irradiation for commercial ginseng powders. White and red ginseng powders were contaminated by about $10^5\;CFU/g$ of total bacteria and by $10^3\;CFU$ of coliforms only in white ginseng powder. Data of microbial population for the sterilizing effect of electron beam irradiation showed that no microorganisms were detected in the samples irradiated up to 7.5 kGy for total aerobic bacteria and 2.5 kGy for molds and coliforms. Such doses were effective for controlling the microbial growth in the samples during 4 months of storage at room temperature. Decimal reduction doses $(D_{10}$ value) on the initial bacterial populations were $2.85{\sim}3.75\;kGy$ in electron beam and $2.33{\sim}2.44\;kGy$ in gamma irradiation, which were influenced by the initial microbial loads and the energy applied. Compared with gamma irradiation, electron beam showed a similar result in its sterilizing effect on ginseng powders, suggesting its potential utilization in due time.

• Journal of Food Hygiene and Safety
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• v.13 no.2
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• pp.143-148
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• 1998

The purpose of this study was to determine the kinetics of paralytic shellfish poison (PSP) destruction at various temperature. The toxic digestive gland homogenate of blue mussel (Mytilus edulis), PSP crude toxin, gonyautoxin group and saxitoxin group were heated at temperature ranging from 90 to $120^{\circ}C$, and then the toxicities were measured in samples heated for various time intervals. The rate constant (k) of the toxic digestive gland homogenate, PSP crude toxin, gonyautoxin group and saxitoxin group were $3.28{\times}10^{-2},\;1.20{\times}10^{-2},\;5.88{\times}10^{-2}\;and\;2.58{\times}10^{-2}\;at\;120^{\circ}C$, respectively. The decimal reduction time (D-value) of the toxic digestive gland homogenate, PSP crude toxin, gonyautoxin group and saxitoxin group were 70, 192, 39 and 89 at $120^{\circ}C$, respectively. These results indicate that PSP crude toxin is most heat-stable of 4 types of PSP toxins and PSP toxin are more heat-stable than food poisoning bacteria and spores. The retorting condition to reduce PSP toxicity below quarantine limit ($80\;\mu\textrm{g}/100\;g$ in Korea and America, 4 MU/g in Japan) could be calculated by rate constant. For example, the digestive gland homogenate having a initial toxicity of $200\;\mu\textrm{g}/100\;g$ could have toxicity below quarantine limit when heated at $90^{\circ}C$ for 129 min., $100^{\circ}C$ for 82 min., $110^{\circ}C$ for 48 min. and $120^{\circ}C$ for 28 min. These results suggest that commercial retorting condition ($115^{\circ}C$ for 70 min) in Korea is enough to reduce toxicity below quarantine limit from initial toxicity of $200\;\mu\textrm{g}/100\;g$. From these results, the quarantine limit of PSP-infested shellfish for canning can be level up to raw score of $200\;\mu\textrm{g}/100\;g$.