• Food Science and Preservation
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• v.6 no.4
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• pp.448-455
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• 1999

The starters, 0.3% of Leuconostoc mesenteroides, Lactobacillus brevis and Lactobacillus fermentum, were added in radish juice to process the radish juice by single and mixed cultures. The radish Juice was fermented for 7 days at 25$^{\circ}C$, 20 days at 15$^{\circ}C$, and 36 days at 5$^{\circ}C$. When fermented at 25$^{\circ}C$, the number of lactic acid bacteria in the juice made with mixed culture was higher than that of the single culture. But, juice fermented at low temperatures (15∼5$^{\circ}C$), the addition of starters was not effective, although there were some differences by inoculation strains. Although there was a little differences by inoculation strains, the content of nonvolatile organic acid and L-ascorbic acid were found more in the juice inoculated with lactic acid bacteria than the juice not inoculated. When the single and mixed cultures at the optimal maturity were tested, the significant difference was found at 5% level except the yeasty and moldy smell and the unripe taste. According to the preference test, the mixed-cultured radish juice incubated at 25$^{\circ}C$with Lactobacillus brevis and Leuconostoc mesenteroides were evaluated superior to commercial Dongchimi. As a result, taste and quality of radish juice was improved by addition of starters.

• Journal of Life Science
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• v.25 no.5
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• pp.496-506
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• 2015

This study explored adequate water temperature ranges for maintaining stable water quality in a biofloc- based zero-water exchange culture system. Five experimental tanks with the following temperatures were set up: 10℃, 15℃, 20℃, 25℃, and 30℃. First, a biofloc-based culture system was developed in the experimental tanks; then, the tanks were stocked with goldfish and went without a water exchange for 60 days. Conditions for developing a biofloc-based culture system and stable water quality in low concentrations of inorganic nitrogen compounds at 10℃, 15℃, 20℃, 25℃, and 30℃ were maintained after 17, 26, 43, 68, and 78 days, respectively. Beginning from when the goldfish were stocked in the biofloc-based culture tanks, concentrations of $NH_4{^+}-N$ remained constant and at low levels at 10℃ and 15℃, but they showed a gradual increase at 20℃, 25℃, and 30℃. Concentrations of $NO_2{^-}-N$ and $NO_3{^-}-N$ at 10℃ and 15℃ did not remain at low levels and immediately increased. While $NO_2{^-}-N$ concentrations at above 20℃ remained constant and stable at relatively low levels, $NO_3{^-}-N$ concentrations showed a gradual increase. Conditions of 15℃ and below could not maintain low and stable concentrations of $NO_2{^-}-N$. In the pH range of 4.0 to 6.0, $NH_4{^+}-N$ concentration decreased as the pH rose. However, there was no correlation between pH and $NH_4{^+}-N$ concentration in the pH range of 6.0 to 8.0. These results indicate that pH levels should be kept at pH 6.0 and above to maintain a low and stable concentration of $NH_4{^+}-N$ at above 20℃.

• Korean Journal of Ichthyology
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• v.21 no.1
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• pp.1-6
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• 2009

The effect of water temperature on fasting and post-prandial total ammonia excretion (TAN) of the starry flounder Platichthys stellatus (mean body weigh : $42.4{\pm}3.4g$) was studied. The fasting and post-prandial TAN excretions were measured under three different water temperatures (10, 15 and $20^{\circ}C$) for 24 hours using a recirculating system. In each treatment three replicates were set up and total 45 fish were used. Fish were taken to the indoor aquarium, acclimated over 10 days at three temperatures, and transferred to TAN measuring system for measurements of TAN excretion at the same temperatures. After 3 days of starvation, fasting TAN excretion was measured at each temperature. To investigate post-prandial TAN excretion, fish were hand-fed to satiation level with a commercial diet containing 50.2% crude protein for 7 days, two times daily 08 : 00 and 16 : 00 h. The fasting and postprandial TAN excretion increased with increased water temperature (p<0.05). Mean fasting TAN excretion rates at 10, 15 and $20^{\circ}C$ were 10.9, 11.2 and $12.2mg\;TAN\;kg\;fish^{-1}\;h^{-1}$, respectively. The value at $20^{\circ}C$ was higher than those at 10 and $15^{\circ}C$ (p<0.05), but there was no significant difference between $10^{\circ}C$ and $15^{\circ}C$. Mean post-prandial TAN excretion rates at 10, 15 and $20^{\circ}C$ were 33.0, 43.4 and $55.3mg\;TAN\;kg\;fish^{-1}\;h^{-1}$, respectively. Two peaks of post-prandial TAN excretions were observed, and the second peak was always greater than the first. The post-prandial TAN excretion rate reached to the maximum after 10 hours from the first feeding at $10^{\circ}C$($45.3mg\;TAN\;kg\;fish^{-1}\;h^{-1}$), $15^{\circ}C$ ($64.5mg\;TAN\;kg\;fish^{-1}\;h^{-1}$) and $20^{\circ}C$ ($83.2mg\;TAN\;kg\;fish^{-1}\;h^{-1}$), respectively. The TAN loss for ingested nitrogen at $20^{\circ}C$ (48.8%) was higher than that for $10^{\circ}C$ (43.0%) and $15^{\circ}C$ (45.7%). This study provides empirical data for estimating ammonia excretion and managing culture management of starry flounder under given temperatures.

• Journal of Mushroom
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• v.14 no.3
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• pp.81-89
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• 2016

White button mushroom (Agaricus bisporus) is the most widely consumed mushroom in the world, and domestic consumption is increasing owing to expansion of the westernized diet in recent years. Before 2000, most Korean mushroom farmers cultivated foreign varieties, but recently, Korean breeders are developing hybrid strains using molecular breeding tools. To produce a better mushroom cultivar, we evaluated some traits of button mushroom Agaricus bisporus strains. Mycelial growth rate at different culture temperatures was investigated by 25>20>15>30>$10^{\circ}C$. Recently developed domestic varieties had superior mycelial growth rate compared to the traditionally grown species. In particular, the ASI1338 strain showed excellent mycelial growth rate at different temperatures. Further, we confirmed that ASI1007, ASI1085, ASI1310, ASI1339 were strongly resistant to bacterial brown blotch, whereas ASI1053, ASI1103, ASI1140, ASI1146, ASI1177, ASI1183, ASI1195, ASI1321, ASI1331, ASI1336 were relatively weakly resistant. The average number of days for 16.5, and that for harvest was 5.7; the average yield was 142.7 g/2-kg bag. Mycelial growth rates at 10, 15, 20, $25^{\circ}C$ were similar, but that at $30^{\circ}C$ was lower. The mushroom yield was highly correlated with the number of days for pinheading and harvest.

• Journal of Food Hygiene and Safety
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• v.24 no.3
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• pp.256-261
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• 2009

Bacillus cereus is a gram-positive spore-forming bacterium and produces an emetic or diarrheal syndrome induced by an emetic toxin and an enterotoxin, respectively. In this study, the effect of different types of media, temperature, and time on the sporulation of B. cereus, and thermal resistance of B. cereus spores produced in various temperatures were evaluated. The highest levels of spores were detected when they are produced at $25^{\circ}C$. There were no significant differences in levels of spores produced at $25^{\circ}C$ among culture media and times while levels of spores produced at $43^{\circ}C$ were significantly reduced with the increase of time. However, thermal resistance of B. cereus spores could be affected by incubation temperature. In fact, higher D-values (12.0, 10.1, and 5.9 min for 2,4, and 6 weeks, respectively) of spores produced at $43^{\circ}C$ were observed than did in samples produced at other temperatures (25 and $37^{\circ}C$). D-values of spores were 7.7, 8.2, and 12.0 min when they were produced at 25,37, and $43^{\circ}C$ for 2 weeks, respectively. The sporulation of B. cereus at $25^{\circ}C$ could result in high amounts of spores however the sporulation at $43^{\circ}C$ for 2 weeks could be effective to produce thermal resistant spores.

• Food Science and Preservation
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• v.17 no.4
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• pp.563-570
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• 2010

We sought to ferment wine from mulberry (Morus alba) juice. The soluble solid content was $9.5{\sim}14.5^{\circ}brix$ on day 6 of fermentation, and gradually fell later; sugar was not further consumed when $3^{\circ}brix$ was attained. Alcohol content rose dramatically on day 6 of fermentation, being 4.5% (v/v) at fermentation temperatures of 16C and 18C, 6.5% (v/v) at 20C, and 8.0% (v/v) at 25C, rising further to 10.5~11.5% (v/v) on day 48, at higher culture temperatures. Citric acid, malic acid, and oxalic acid were present in mulberries. The levels of both citric and oxalic acid fell after fermentation, whereas malic acid concentration increased. All of fructose, glucose, maltose, and sucrose were fermented. Electron-donating ability (EDA) was elevated to over 90% of the control value in mulberry juice diluted to 40% (v/v). SOD-like activities in juice and wine were 80.1% and 72.1% of the control value. Nitrite-scavenging abilities (NSAs) were 86.2% and 85.2% of control in undiluted juice and wine, respectively. Mulberry juice had an activation level higher than that of mulberry wine, but functionality neither rose nor fell after fermentation. Insensory evaluation, the overall wine score was better than average, at 5.00, demonstrating the commercial potential of mulberry wine.

• Korean Journal of Food Science and Technology
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• v.48 no.4
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• pp.329-334
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• 2016

The inhibitory effect of epigallocatechin gallate (EGCG), one of the antioxidants in green tea (Camellia sinensis), against Salmonella Enteritidis was evaluated in commercial braised quail eggs at two temperatures (4 and $25^{\circ}C$). Although S. Enteritidis was dose-dependently suppressed by EGCG in pure culture at $25^{\circ}C$, it was not inhibited in the sauce or eggs at this temperature. At low temperature ($4^{\circ}C$), S. Enteritidis was inhibited in both the sauce and eggs by $400{\mu}g/mL$ EGCG. Thus, EGCG at an appropriate concentration could be a useful food additive for inhibiting S. Enteritidis in braised quail eggs at low temperatures.

• Microbiology and Biotechnology Letters
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• v.31 no.1
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• pp.63-68
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• 2003

Saccharomyces cerevisiae KNU5377 is a constitutively thermotolerant, fermentative strain at high temperatures over 4$0^{\circ}C$. The exposure to 0.5 M NaCl caused S. cerevisiae KNU5377 to be lost its constitutive thermotolerance. Furthermore, the NaCl adaptation beyond 0.3 M during the overnight culture forced the strain-specific fermentation ability of S. cerevisiae KNU5377 to be disappeared. However, these phenomena did not occur in the reference, Saccharomyces cerevisiae ATCC24858. As a result, this adaptation led both strains to show the closely similar thermotolerance level and alcohol fermentation ability, implying the NaCl adaptation eliminated its strain-specific characteristics of S. cerevisiae KNU5377 Therefore it indicated that the superior intrinsic characteristics of S. cerevisiae KNU5377 must be related to the NaCl adaptation. On the other hand, the heat adaptation elevated alcohol productivity for both strains, but surprisingly did it for KNU5377 at the rate of two times higher than the reference's one; this suggests that KNU5377 possesses more efficient system enough to cause the difference. Consequently, these characteristics of S. cerevisiae KNU5377 must be interesting targets for further study to understand on how KNU5377 could acquire the constitutive thermotolerance and the outstanding fermentative capacity at high temperatures.

• Korean Journal of Microbiology
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• v.34 no.4
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• pp.212-218
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• 1998

An obligately methylotrophic bacterium which produces extracellular polysaccharide (EPS) was isolated through methanol-enrichment culture technique. The isolate was aerobic, nonmotile, and gram negative rod and exibited catalase, but no oxidase, activity. Plasmid, carotenoid, and poly-${\beta}$-hydroxybutyric acid were not found. The guanine plus cytosine content of DNA was 52-56%. The isolate was found to grow only on methanol and monomethylamine. Growth was optimal ($t_d=2.4h$) at $35^{\circ}C$ and pH 6.5 in a mineral medium containing 0.5% (v/v) methanol, 25 mM phosphate, and 0.212% ammonium sulfate. Methanol was assimilated through the ribulose monophosphate pathway. Maximun amount of EPS was produced in cells growing at the mid-stationary growth phase at $30^{\circ}C$ in a mineral medium (PH 6.5) containing 1.0% (v/v) methanol in the CIN ratio of 54.7. Thin-layer chromatographic and high performance liquid chromatographic analysis revealed that the EPS was composed of glucose and galactose. EPS which was not treated with ethanol (Pbe) exhibited stable viscosity under various concentrations of salts and temperatures hut showed high viscosity at low pH. EPS precipitated with ethanol (Pae) was found to be more stable in viscosity than the Pbe at various salt concentrations, temperatures, and pH. The Pae also exhibited higher viscosity than the Pbe and xanthan gum. Scanning electron microscopy revealed that the lyophilized Pbe and Pae have a multi-layered structure and a structure of thick fibers, respectively.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.3
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• pp.49-82
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• 1965

For the stable and high yields of low-land rice in Korea, the characteristics of rice plant for the vegetative and physiological responses, plant type formation, and yield components have been studied in order to obtain the fundamental data for the improvement of cultural practices, especially for the ideal fertilizer application. Furthermore the environmental conditions in Korea including temperatures, light, precipitation, and soil conditions have been compared in the broad sense with those in Japan, and the application of nitrogen, phosphorus, potassium, silicate and other micro-nutrients were described in relation to the characteristics of environmental conditions for the improvement of fertilizer application. 1. The average yield of polished-rice per 10 are in Korea is about 204 kg and this values are much less than those in Japan and Taiwan where they produce 77% to 13% more than in Korea. The rate of yield increase a year in Korea is 4.2 kg, but in Japan and Taiwan the rates of yield increase a year are 81 % and 62%, respectively. It was also found that the coefficient of variation of yield is 7.7% in Korea, 6.7% in Japan and 2.5% in Taiwan. This means that the stability of producing rice in Korea is very low when compared with those in Japan and Taiwan. 2. It was learned from the results obtained from the 'annual yield estimation experiment' that there are big differences in the respect of plant type formations between rice crops grown in Japan and Korea. The important differences found were as follows: (1) The numbers of spikelets per 3.3 square meters are 891 in Korea and 1, 007 in Japan(13% more than in Korea). (2) The numbers of tillers per 3.3 square meters at the stage of maximum tillering are 1, 150 in Korea, but in Japan they showed 19% more than in Korea. (3) The ratio of effective tillers to total tillers is 77.5% in Korea and 74.7% in Japan, which seems to be higher in Korea than in Japan. But the ratio in Korea is very low when considered the numbers of total tillers in both countries. (4) The ratio of grain to straw is 85.4% in Korea and 96.3% in Japan. 3. The average temperatures during the growing season at the area of Suwon, Kwangjoo and Taegu are almost same as those in the district of Jookokoo(Fookoo yama) in Japan, i.e., the temperatures during the rice-growing season in Korea are similar to those in the southern-warm regions of Japan. 4. Considering the minimum temperatures at the stage of limiting transplanting, 13$^{\circ}C$, the time of transplanting might be 30 to 40 days earlier than presently practicing transplanting time, which comes around June 10. 5. The temperatures during the vegetative growth in Korea were higher than those temperatures that needed in the protein synthesis which ate the main metabolism during this stage. However, the temperatures at the time of reproductive growth was lower than the temperatures that needed in the sugar assimilation which is main metabolism in this stage. In this point of view, it might be considered that the proper time of growing rice plant in Korea would be rather earlier. 6. The temperatures and the day light conditions at the time of first tillering stage of rice plant, when planted as presenting transplanting practices, are very satisfactory, but the poor day light length, high temperatures and too wet conditions in the time of last-tillering stage(mid or last July) might cause the occurrence of disease such as blast. 7. The heading stage of rice plants at each region through nations when planted as presently practicing method comes when the day light length is short. 8. It was shown that the accumulated average air-temperature at the time of maturing stage was not enough and the heading time was too late, when considered the annual deviations of mean temperatures and low minimum temperatures. 9. The nitrogen content of each plant part at the each growing stage was very high at the stage of vegetative growth when compared with the nitrogen content at the stage of reproductive growth after heading. In this respect it was believed to be important to prevent the nutrient shortages at the reproductive stages, especially after the heading. 10. The area of unsatisfactory irrigation paddy fields and natural rain-fed paddy fields are getting reduced in Korea. The correlation between the rate of reducing unsatisfactory irrigation and natural rain-fed paddy fields and the rate of yield increase were computed. The correlation coefficients(r) between the area of unsatisfactory irrigation paddy fields and yield increase were +0.525, and between the natural rain-fed paddy fields and yield increase, +0.832 and between the unsatisfactory irrigation plus natural rain-fed paddy fields and yield increase, +0.84. And there were. highly significant positive correlations between natural rain-fed paddy fields and yield increases indicating that the less the area of natural rain-fed paddy fields, the greater the yields per unit area. 11. The results obtained from the fertilizer experiments (yield performance trials) conducted in both Korea and Japan showed that the yield of non-fertilized plots per 10 are was 231 kg in Korea and 360 kg in Japan. On the basis of this it might be concluded that the fertility of soil in Korea is lower than that in Japan. Furthermore it was. also found that the yields of non-nitrogen applied plots per 10 are were 236 kg in Korea and 383 kg in Japan. This also indicates that the yields of rice in Korea are largely depending on the nitrogen content in the soil. 12. The followings were obtained when the chemical natures of soils in both Korea and Japan were compared. (1) The content of organic matter, total nitrogen, exchangeable calcium, and magnesium in Korea were no more than the half those in Japan. (2) The content of N/2 chloride and soluble silicate in low-land soil were on the average lower in Korea. (3) The exchange capacity of bases in Korea was no more than half that in Japan. 13. It was also observed by comparing the soil nature of the soil with high yielding capacity with the soil with low yielding capacity that the exchange capacity of bases, exchangeable calcium and magnesium, potassium, phosphorus, manganese, silicate and iron were low in the soil with low yielding capacity. 14. The depth of furrow slice was always deeper in the soil with high yielding capacity, and the depth of furrow slice in Korea was also shallower than that in Japan. 15. Summarizing the various conditions mentioned previously and considering the effects of silicate and trace elements such as manganese and iron besides three elements on the physiological and plant type formation of rice crops, more realistic and more ideal fertilizing practices were proposed. proposed.