• Journal of the Korean Society of Food Culture
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• v.35 no.5
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• pp.450-458
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• 2020

This study examined the optimal temperature and time conditions to maintain high quality Dongchimi during the fermentation and storage period. Dongchimi was fermented at low (5℃), medium (10 and 15℃), and high (20℃) temperatures until the acidity reached 0.2, 0.3, and 0.4%. respectively. From the consumer's preference test enrolling five consumers, Dongchimi fermented at 15℃ until an acidity of 0.3% (for approximately six days) was evaluated to be the optimal status because of its high score of overall acceptance, taste, and odor of consumers. To determine the optimal storage temperature of fermentation, Dongchimi was stored at three different temperatures (-1, 2, 5℃) for four weeks after fermenting at 15℃ for six days. During the storage period, most of the physicochemical properties (pH, acidity, reducing sugar content, and organic acid) and microbiological properties changed significantly in the 2 and 5℃ groups, resulting in a significant change in descriptive sensory analysis of Dongchimi. These results indicate that fermentation at 15℃ and storage at -1℃ for Dongchimi enables it to maintain the best quality for a long time.

• Korean Journal of Food Science and Technology
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• v.16 no.4
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• pp.443-450
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• 1984

Chemical and microbial changes during Kimchi (a group of Korean seasoned pickles) fermentation were carried out at various temperatures and salt concentrations. The time reaching optimum ripening of Kimchi varied depending upon fermentation temperature and salt concentration. At high temperature and low salt content Kimchi fermentation was faster than at low temperature and high salt content. The ratio of volatile to non-volatile acids reached its maximum at the optimum ripening time of Kimchi and decreased thereafter. Leu. mesenteroids, Lac. brevis, Lac. plantarum, Ped. cerevisiae, Str. faecalis and low acid producing Lactobacilli were isolated from Kimchi samples. However, the main microorganism responsible for Kimchi fermentation was Leu. mesenteroides and Lac. plantarum was the main acidifying organism. Total viable count increased rapidly in the beginning of fermentation and reached its maximum number at optimum ripening time and then decreased slowly as the acidity of Kimchi increased. While the total aerobic bacteria and fungi decreased during Kimchi fermentation, the yeast increased significantly at lower temperature.

• Journal of the Korean Society of Food Science and Nutrition
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• v.24 no.5
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• pp.752-757
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• 1995

The effect of fermentation temperature on the changes of pH, acidity, salt content, color and vitamin C of mustard leaf kimchi during various storage days was investigated. The conditions of fermentation temperature were set at $4^{\circ}C$ (sample A) and $20^{\circ}C$ (sample B), and $4^{\circ}C$ after keeping at $20^{\circ}C$ for 12 hours(sample C) and $20^{\circ}C$ for 36 hours(sample D). As the fermentation proceeded, pH of sample stored at low temperature(sample A) was drop ped gradually from initial pH of 5.24 but there was great pH drop in the sample stored at high temperature(sample B, D). The salt content of the sample B at high temperature increased remarkably, and then the values showed D > A > C. The Humter values of L and a increased at the optimum ripening period, the higher the initial fermentation temperature(B) and the later the initial fermentation time at $20^{\circ}C$ those values, then decreased. The Hunter value of b constantly increased until day of 108. As fermentation time passed, the content of total vitamin C decreased to the range of 9.0mg% to 14.0mg% up to 24 days of fermentation, and at the optimum ripening period, it increased to the range of 14.0mg% to 22.0mg%, and at the fermentation period(until day 108), it decreased gradually.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.6
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• pp.1021-1027
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• 1997

$CO_2$production in fermentation of dongchimi was measured and interrelated with changes in pH and titratable acidity. The effects of salt content and temperature on $CO_2$production rate were analysed. Fermentation of dongchimi showed drastic pH decrease in early stage and subsequent levelling off around 3.9, with linearly increased acidity up to 0.3~0.4% optimum quality. $CO_2$production of dongchimi could be analysed to consist of two consecutive stages of constant rate. The first stage $CO_2$production of higher rate moved to the second stage of lower rate when acidity rose beyond 0.3%. When compared to those of 1 and 2% salt content, dongchimi of 3% salt showed lower $CO_2$production rate in the 1st stage and slower acidity change through the whole fermentation period. However, it resulted in the product of highest $CO_2$accumulation at optimal ripeness because of consistent $CO_2$production of longer 1st stage period and relatively high $CO_2$production rate in 2nd stage. $CO_2$production depended on temperature less compared to acidity change(activation energy: 57.3 and 44.3kJ/mol for $CO_2$production of 1st and 2nd stages, respectively; 79.3kJ/mol for acidity change), which means higher ratio of $CO_2$production rate relative to acidity increase at lower temperature. Slower increase in acidity at low temperature also was shown to extend the period of 1st stage $CO_2$production. Therefore, low temperature fermentation was effective in producing the high $CO_2$content dongchimi at adequate acidity, which is desirable organoleptically.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.5
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• pp.800-806
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• 1997

Effect of temperature on Kakdugi during fermentation was investigated by measuring sensory, physicochemical and microbiological, properties up to 57 days. The diced(2.5$\times$2.5$\times$2.5cm) Chinese radishes(Ra-phanus sativus L.) with other ingredients were fermented under the different temperatures. Kakdugi were stored at 4$^{\circ}C$ after keeping at 2$0^{\circ}C$ for 12 hours(treatment E) from initial fermentation to the end at each temperature on preparation. The pH was decreased to the range of 4.14~4.29 in the initial of pH 5.8, and total acidity was increased 2~4 times more than that of in the initial period (0.24%). And the changes of treatment A, B, and C were nearly constant up to 57 days in the range of 0.80~0.88% (pH 4.1). The changes of vitamin C showed sigmoidal curve, increasing significantly in the palatable period after decreasing gradually in the initial period. The content of vitamin C in treatment E was rapidly decreased, but that of treatment C was kept high content up to 57days. the number of lactic acid bacteria was remarkably increased in palatable period and was gradually decreased thereafter. The scores of aroma, taste, overall acceptability in sensory evaluation during the fermentation was high in order of treatment E, C, D, B and A. The scores of sensory evaluation treatment D and E during fermentation was rapidly decreased, however, treatment A, B and C were maintained. Changes of lactic acid bacteria, and sensory properties, among treatment A, B and C which kept a good quality up to 57 days, had high scores of sensory evaluation, abundant vitamin C in the palatable period. The result showed that Kakdugi fermented at 4$^{\circ}C$ after keeping at 2$0^{\circ}C$ for 36 hours had better taste and quality than those of other treatments.

• Preventive Nutrition and Food Science
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• v.4 no.4
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• pp.236-240
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• 1999

The characteristics of natural lactic acid fermentation of radish juice were investigated at different salt concentrations (0~2%) and temperatures (10~3$0^{\circ}C$). Major lactic acid bacteria isolated from the radish juice fermented at 2% slat concentration were Leuconostoc mesenteroides, Lactobacillus plantarum, and Lactobacillus brevis. The percentage of lactic acid bacteria against total microbe in the fermented radish juice was over 80% at 0~1% salt concentrations, suggesting the possibility of fermentation even at low salt concentration, but was still active even at 1$0^{\circ}C$. The time to reach pH 4.0 during fermentation of juice of 1% salt concentration was 281~301 hrs at 1$0^{\circ}C$ and 50-73 hrs at 3$0^{\circ}C$. The concentrations of sucrose and glucose in the fermented juice were low at high temperatures and were the lowest at a 1.0% salt concentration. However, the content of mannitol showed the opposite trend. Although sour taste, ripened taste, and acidic odor of the fermented juice showed no significant differences among various temperatures and salt concentrations, sensory values of ripened taste and sour acidic were high at high temperatures. The overall quality was the best at 1.0% salt concentration, irrespective of the temperature.

• Microbiology and Biotechnology Letters
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• v.24 no.6
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• pp.726-732
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• 1996

To improve the fermentation characteristics(such as starch-degradability, ethanol tolerance, sugar and high-temperature tolerance) of recombinant haploid yeast Saccharomyces diastaticus K114, hybridization technique was used. The hybridization partner was S. diastaticus 1177 which had good glucoamylase activity and fermentabi- lity. The best hybrid HH64 showed improved ethanol tolerance, sugar and high-temperature tolerance. Especia- lly, the starch-fermentability was significantly improved, since the hybrid produced 1.60% (w/v) ethanol from 4% (w/v) starch, while the recombinant haploid K114 produced 1.30% (w/v) ethanol. The optimum temperature and pH for the starch-fermentation by the hybrid HH64 was 30$\circ$C and 5, respectively. The hybrid yeast HH64 produced 7.5% (w/v) ethanol directly from 20% (w/v) starch.

• Journal of the Korean Society of Food Culture
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• v.16 no.5
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• pp.431-441
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• 2001

To develop the low-temperature and long-term fermented kimchi, kimchi was prepared according to the recipe of a specific ratio of major and minor ingredients and adjusted its salinity to 3.7%. Prepared kimchi fermented at $15{\pm}1^{\circ}C$ for 24 hours and transferred and fermented in a refrigerator only used to make low-temperature and long-term fermented kimchi at $-1{\pm}1^{\circ}C$ for 30 weeks. During 30 weeks of fermentation the changes in physicochemical and microbiological properties of low-temperature and long-term fermented kimchi were studied. The initial pH of 6.47 decrease gradually and dropped to pH 4.0 after 14 weeks of fermentation, and then it maintained at same level. Acidity increased to 0.49% on 2 weeks of fermentation and kept at 0.47 $\sim$0.50% during 2 to 30 weeks fermentation. Salinity was slightly increased at early stage and started to decrease on 4 weeks of fermentation, and then it did not change. The change of reducing sugar content was closely related to the trend of pH change with a very high correlation coefficient(r =0.912). Lactic acid, citric acid, malic acid, succinic acid and acetic acid were major organic acids contained in low-temperature and long-term fermented kimchi. Vitamin C content decreased at initial stage of fermentation and then slightly increased up to the maximum of 22.3 mg% on 8weeks of fermentation. In color measurement, L value continued to increase during the fermentation and reached at the highest of 55.45 on 22 weeks of fermentation, and a and b values of 3.62 and 4.54 also increased to 31.26 and 37.32 on 30 weeks of fermentation, respectively. Total microbial count increased slowly from beginning and was the highest on 4 weeks of fermentation, and then began to decrease slowly. Count of Lactobacillus spp. was highest after 6weeks, but count of Lactobacillus spp. was highest on 2 weeks of fermentation, and then both showed a slow decrease. Yeast count wasn't increased until 4 weeks of fermentation and then increased rapidly to get the highest on 10 weeks of fermentation.

• Microbiology and Biotechnology Letters
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• v.23 no.5
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• pp.624-631
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• 1995

The fermentation characteristics of Saccharomyces cerevisiae F38-1, a newly isolated thermotolerant yeast strain from a high temperature environment have been studied using a fermentation medium containing 20% glucose, 0.2% yeast extract, 0.2% polypeptone, 0.3% (NH$_{4}$)$_{2}$SO$_{4}$, 0.1% KH$_{2}$PO$_{4}$, and 0.2% MgSO$_{4}$ without shaking at 30$\circ$C to 43$\circ$C for 5 days. The fermentability was over 90% at 30$\circ$C, 88% at 37$\circ$C, 77% at 40$\circ$C and 30% at 43$\circ$C. A similar fermentation result was obtained at pH between 4 and 6 at 30$\circ$C and 40$\circ$C. Aeration stimulated the growth of the strain at the beginning of the fermentation, but it reduced alcohol production at the end of alcohol fermentation. Optimal glucose concentration was determined to be between 18 and 22% at 40$\circ$C as well as 30$\circ$C, but the growth was inhibited at the glucose concentration of over 30%. A fermentability of over 90% was observed at 40$\circ$C in 2 days when the medium was supplemented by 2% yeast extract. A higher inoculum size increased the initial fermentation rate, but not the fermentation. A fermentability of over 90% was achieved in 2 days at 40$\circ$C in a fermentor experiment using an optimized medium containing 20% glucose and 1% yeast extract.

• Biotechnology and Bioprocess Engineering:BBE
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• v.8 no.3
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• pp.179-182
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• 2003

Anaerobic fermentation was attempted to produce methane from the wood chip (Eucalyptus globulus). By the pretreatment of the wood chip using hot water with high temperature, NaOH, and steam explosion, the production of methane gas was enhanced. The pretreatment using Steam explosion resulted in more amount of methane gas produced than the treatment using either hot water or 1% (w/w) NaOH with high temperature, and the steam explosion at a steam pressure of 25 atm and a steaming time of 3 min was the most effective for the methane production. The amount of methane gas produced depended on the ratio of weight of Klason lignin, a high molecular weight lignin, in the treated wood chip.