• Food Science of Animal Resources
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• v.29 no.3
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• pp.310-316
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• 2009

In this study, the influence of pressure assisted mild thermal inactivation (PAMTI) on E. coli ATCC 10536 was examined at 200 MPa and temperature range of $20-50^{\circ}C$. Inactivation rate significantly increased (p<0.05) as temperature and time increased at 200 MPa. The maximum inactivation (7.91 log reduction) was obtained at $50^{\circ}C$ for 30 min under 200 MPa, which meant the complete inactivation of E. coli ATCC 10536. Inactivation kinetics were evaluated with the first order inactivation rate (k), activation energy ($E_a$), thermal death time (TDT), and z value. Kinetic parameters were significantly (p<0.05) influenced by variation temperature of PAMTI. In this study, the synergistic effect of pressure and temperature were found in the inactivation of E. coli ATCC 10536 through PAMTI.

• 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.29 no.6
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• pp.1202-1207
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• 1997

Inactivation of Leuconostoc sp. isolated from kimchi using carbon dioxide under pressure was investigated in terms of operating parameters in order to evaluate its feasibility as a novel nonthermal process. Inactivation rates increased with increasing pressure, temperature and exposure time, but with decreasing working volume. Microbial reduction of 3 log cycles was achieved within 150 min under a $CO_2$ pressure of $60\;kg/cm^2$ at 30^{\circ}C$. It was confirmed that microbial inactivation by the high pressure $CO_2$ was governed essentially by the characteristic of $CO_2$ mass transfer and thus penetration of $CO_2$, into cells was a rate limiting step to determine efficiency of the inactivation process. The experimental results suggested that the high pressure $CO_2$ treatment could be used as one of the effective nonthermal methods for preserving foods.

• Food Science and Biotechnology
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• v.18 no.4
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• pp.861-866
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• 2009

Effects of pressure come-up and holding times on the inactivation of Salmonella enterica and Listeria monocytogenes were evaluated in deionized water, milk, orange juice, and tomato juice with pH 6.76, 6.85, 3.46, and 4.11, respectively. The inoculated samples were subjected to high pressure treatments at 300, 400, and 500 MPa for less than 10 min at $30^{\circ}C$. At 500 MPa, the numbers of S. enterica and L. monocytogenes in deionized water, orange juice, and tomato juice were reduced by more than 6 log CFU/mL during the come-up time. Compared to orange and tomato juices, milk showed a considerable baroprotective effect against S. enterica and L. monocytogenes. At 300 MPa, the D values for S. enterica in milk, orange juice, and tomato juice were 0.94, 0.41, and 0.45 min, while those for L. monocytogenes were 9.56, 1.11, and 0.94 min, respectively. Low pH resulted in a noticeable synergistic effect on the inactivation of S. enterica and L. monocytogenes in orange and tomato juices. Therefore, these results might provide more useful information for designing the entire high hydrostatic pressure (HHP) conditions, taking the come-up time reduction, and food system.

• Journal of Microbiology and Biotechnology
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• v.17 no.3
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• pp.524-529
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• 2007

Pressure inactivation behavior of Bacillus amyloliquefaciens spores was investigated in deionized water. The spores of B. amyloliquefaciens were subjected to $105^{\circ}C$ and 700 MPa. The magnitude of the decrease in viability after pressure treatment was similar to that after pressure treatment followed by heat shock. The increase of dipicolinic acid (DPA) release was correlated with the spore inactivation, and the hydrophobicity did not significantly change during the pressure-assisted thermal processing (PATP). Lag phase duration increased with increasing pressure process time. The mechanisms of spore germination and inactivation during the PATP were related to a complex physiological process.

• Food Science and Biotechnology
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• v.16 no.2
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• pp.255-259
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• 2007

The effects of temperature heating-up rate and pressure building-up phase on the inactivation of Listeria innocua ATCC 33090 were evaluated in buffered peptone water. The number of L. innocua was reduced by 5.57 and 6.52 log CFU/mL during the nonisothermal treatment (the come-up time followed by isothermal process) and the isothermal treatment, respectively, at $60^{\circ}C$. When compared to the isothermal treatment (0.76$33.2^{\circ}C/min$ of temperature heating-rate. The effect of the combined high pressure and thermal processing on the inactivation of L. innocua increased with increasing pressure and temperature. At all temperature levels from 40 to $60^{\circ}C$ under 700 MPa, L. innocua was not detected by enrichment culture (>7 log reduction).

• Food Engineering Progress
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• v.15 no.4
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• pp.318-323
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• 2011

High pressure processing (HPP) technology was applied to inactivate the microorganisms in Doenjang (soybean paste) and the effects of salt concentration on the HPP inactivation of microorganisms were analyzed. The microorganisms in Doenjang containing low salt content showed greater sensitivity to HPP than those with high salt content. HPP inactivation effects decreased as salt concentration of Doenjang increased. The HPP sensitivity decreased in the order of fungi, yeasts, bacteria in terms of microorganism type. The HPP of Doenjang at 6,500 atm for 40 min inactivated most yeasts and fungi, indicating that the HPP technology was applicable to control the microorganisms in Doenjang, especially with a low level of salt.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 2006.05a
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• pp.277-280
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• 2006

This study was carried out to investigate the effect of HPLT on the inactivation rates of microorganisms in raw milk depending on the pressurization time and temperature. Raw milk samples were submitted to HPLT of 200 MPa at -4, 4, 12 and $20^{\circ}C$, respectively. Inactivation increased with pressurization time and HPLT of microorganisms at 200 MPa was time dependent at any temperature. At sub-zero temperature of $-4^{\circ}C$, high pressure pasteurization was the most effective in inactivating microorganisms.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 2006.05a
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• pp.329-332
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• 2006

This study was carried out to investigate the effect of high pressure low temperature (HPLT) on the inactivation rates of S. cerevisiae in 0.9% saline solution depending on the pressurization time and temperature. S. cerevisiae was inoculated with UHT milk and submitted to HPLT of 200 MPa at 4, 12 and $20^{\circ}C$, respectively Inactivation increased with pressurization time and HPLT of S. cerevisiae at 200 MPa was time dependent at any temperature. The morphological changes of yeast cells observed with a SEM after HPLT.

• Journal of Life Science
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• v.21 no.8
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• pp.1094-1099
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• 2011

Antimicrobial efficacy of high pressure (HP) can be enhanced by the application of additional hurdles. The objective of this study was to assess the enhancement in pressure lethality by tert-butylhydroquinone (TBHQ) treatment, against bacterial spores that are considered significant in the food industry. Spores of Clostridium sporogenes, Bacillus cereus and B. subtilis were prepared. Spore suspensions containing TBHQ (200 ppm, dissolved in dimethyl sulfoxide, DMSO) were pressurized at 650 or 700 MPa at 54-72$^{\circ}C$ for 5 min. Inactivation of bacterial spores resulted only with HP treatment. The population of B. subtilis spores was more inactivated by HP than those of B. cereus and C. sporogenes spores. Inactivation of C. sporogenes spores using pressure was more affected by the germinated population, compared to Bacillus spores. The inactivation of Bacillus spores increased when pressurized at 70$^{\circ}C$, compared to 54$^{\circ}C$. On the other hand, the degree of germination-induced lethality for Bacillus spores decreased at 70$^{\circ}C$. When spores were treated with a combination of DMSO-HP and TBHQ-HP, these treatments seemed to protect the spores against HP, especially at 54$^{\circ}C$. Further mechanistic studies involved in inducing germination by HP and using a subsequent sporicidal agent will be needed for a better understanding of bacterial spore inactivation.