• Korean Journal of Food Science and Technology
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• v.53 no.3
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• pp.329-333
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• 2021

Subcritical water extraction (SWE) is an eco-friendly extraction method that uses only purified water as a solvent under high temperature and high pressure conditions. In this study, total phenolics, and antioxidant activity were evaluated in Ziziphus jujuba Mill extracts from subcritical water obtained by varying the extraction temperature (110-190℃) and extraction time (1-20 min). Total phenolics was maximized with extraction at 190℃ for 15 min (67.79±3.45 mg gallic acid equivalent/g jujube). The 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity (48.84±4.74%) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) free radical scavenging activity (84.75±1.15%) were maximal at extraction conditions of 190℃, for 20 min. All jujube extracts prepared using SWE had higher total phenolics and antioxidant activities than extracts prepared using organic solvent extraction (60℃, 120 min), including methanol and ethanol. SWE could be an excellent alternative to organic solvents for extracting phenolics and antioxidant compounds.

• Mycobiology
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• v.45 no.4
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• pp.240-254
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• 2017

Cereal grains are the most important food source for humans. As the global population continues to grow exponentially, the need for the enhanced yield and minimal loss of agricultural crops, mainly cereal grains, is increasing. In general, harvested grains are stored for specific time periods to guarantee their continuous supply throughout the year. During storage, economic losses due to reduction in quality and quantity of grains can become very significant. Grain loss is usually the result of its deterioration due to fungal contamination that can occur from preharvest to postharvest stages. The deleterious fungi can be classified based on predominance at different stages of crop growth and harvest that are affected by environmental factors such as water activity ($a_w$) and eco-physiological requirements. These fungi include species such as those belonging to the genera Aspergillus and Penicillium that can produce mycotoxins harmful to animals and humans. The grain type and condition, environment, and biological factors can also influence the occurrence and predominance of mycotoxigenic fungi in stored grains. The main environmental factors influencing grain fungi and mycotoxins are temperature and $a_w$. This review discusses the effects of temperature and $a_w$ on fungal growth and mycotoxin production in stored grains. The focus is on the occurrence and optimum and minimum growth requirements for grain fungi and mycotoxin production. The environmental influence on aflatoxin production and hypothesized mechanisms of its molecular suppression in response to environmental changes are also discussed. In addition, the use of controlled or modified atmosphere as an environmentally safe alternative to harmful agricultural chemicals is discussed and recommended future research issues are highlighted.

• Journal of Korean Society on Water Environment
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• v.24 no.3
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• pp.280-284
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• 2008

Efficacy of antifungal activity on plant pathogens by compost teas fermented under different temperatures was studied. Compost teas are recently chosen by agricultural producers for the better method of controlling plant diseases under increase of public consciousness against use of chemicals for controlling the diseases. Compost tea has been intensively studied; however, understanding of compost tea is still not well developed, and temperature influence during fermentation of compost tea on its antifungal activity has not been investigated. In this study, antifungal activities of compost teas fermented at 10, 20, 30, and $40^{\circ}C$ against selected 10 pathogens were observed. From the results, antifungal activities of compost teas at 20 and $30^{\circ}C$ of fermentation-temperatures showed the strongest while the weakest activity was observed with the compost tea at $10^{\circ}C$. Change of the activity by the fermentation-temperature apparently implied that microbes in the compost tea were strongly involved in its antifungal activity.

• Korean Journal of Medicinal Crop Science
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• v.17 no.6
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• pp.407-411
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• 2009

Hepatoprotective and antioxidant activities of Acer mono and A. okamotoanum were compared after being extracted by low temperature and high pressure (LTHP) at 20 MPa and $60^{\circ}C$ for 15 minutes. Extraction yield of both A. mono and A. okamotoanum was increased about 40~43% by this extraction process. On scavenging activities, the bark of A. okamotoanum from this extraction process showed the highest activity as about 97%. This value was higher than that from conventional water extraction and A. mono extracts. Both of A. mono and A. okamotoanum showed high ability on nitrite scavenging, but decreasing tendency according to increasing of pH. On SOD-like test, A. okamotoanum had the highest activity as 46.28% at $1.0\;mg/m{\ell}$ concentration. A. okamotoanum extracted by LTHP also showed the highest activity as 197.38% in adding $1.0\;mg/m{\ell}$ concentration. Generally, the extracts from low temperature and high pressure extraction process are higher hepatoprotective and antioxidant activities than that from conventional water extraction. It can conclude that the bark of A. okamotoanum has better biological activities than other parts of A. mono.

• Korean Journal of Food Science and Technology
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• v.27 no.4
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• pp.532-536
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• 1995

Effect of water activity $(0.32{\sim}0.89)$ on the physicochemical properties of sweet potato starch during the storage for 5, 15 and 30 days at $40^{\circ}C$ was investigated. Shapes and sizes of starch granules were not changed. X-ray diffraction patterns of the starches appeared equally Ca-crystal structure. Sorption isotherm with storage day was sigmoidal. A slight loss of iodine affinity, increase in water binding capacity, and decrease in swelling power at $80^{\circ}C$ occurred as water activities increased. Viscosity pattern under Brabender Amylogram was not significantly changed with water activity, but initial pasting temperature decreased as water activity increased. The viscosity at $50^{\circ}C$, consistency and setback were increased with increasing storage day and water activity.

• Korean Journal of Pharmacognosy
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• v.51 no.3
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• pp.199-206
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• 2020

The aim of this study was to investigate the potential of Chaenomeles sinensis as a content of protocatechuic acid and physiological activities. The analyzed the content of protocatechuic acid of Chaenomeles sinensis water extract (CSW) according to different extract temperature and time for extraction. It was analyzed as 0.14±0.00 mg/g in the extract at 100℃ for 3 h. Protocatechuic acid content increased as extraction time and temperature increased. The activity of the CSW at 100℃ for 3 h was measured. As a result of measuring DPPH, ABTS radical scavenging activity and SOD activity, antioxidant activity was found and α-glucosidase inhibition activities. Cell viability was shown for RAW 264.7 cells, and NO (nitric oxide) production was also inhibited. Finally, content of protocatechuic acid increased with increasing extraction time and extraction temperature, and exhibited antioxidant activity, inhibition of NO production, and anti-diabetic activity. It is believed that the Chaenomeles sinensis is likely to be developed as a functional material.

• Korean Journal of Food Science and Technology
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• v.26 no.4
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• pp.370-374
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• 1994

The effect of water activity(Aw) and storage temperature on retrogradation of pregelatinized corn starch was investigated at various temperature of $4^{\circ}C$, $20^{\circ}C$ and $30^{\circ}C$. Samples stored at different water activity, i.e., 0.43, 0.52, 0.75, 0.83, 0.88 and 0.93 by means of saturated salt solutions. The rate of retrogradation was determines. by enzymic digestibility, and evaluated by Avrami equation. The degree of retrogradation during storage showed a great difference around Aw 0.8. At Aw 0.52 and 0.75 at all temperatures, retrogradation occurred slightly. The effect of water activity on retrogradation was much greater at $4^{\circ}C$ than 300. And at Aw 0.43, the degree of retrogradation after 3-week storage was smaller than 3.9%. The critical water activity of retrogradation was inferred as Aw 0.43. At each temperature, the degrees of retrogradation of gelatinized corn starch after 24-day storage were 30% at Aw 0.8 and Aw 0.9, and greater than 50% at the Aw above 0.9. At Aw below 0.8 the degree of retrogradation was about 20%. The rate constants of retrogradation according to Aw showed small differences at $20^{\circ}C$ and $30^{\circ}C$, but showed a great difference at $4^{\circ}C$. The value of exponent of Avrami was 1.0 regardless of temperature and water activity. And the rate constants of retrogradation increased with increasing Aw, but decreased with increasing temperature.

• The Korean Journal of Food And Nutrition
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• v.33 no.1
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• pp.64-73
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• 2020

The purpose of this study was to investigate the antioxidant activity and β-glucan content of extracts extracted by varying the temperature at 30, 55 and 80℃ after hot air drying or freeze drying of Pleurotus ostreatus and Pleurotus eryngii. For the analysis antioxidant activity of each mushroom, β-glucan, total phenol, flavonoid contents, and DPPH·ABTS⁺·Nitrite assay were measured. Also, the β-glucan content, total flavonoid content and ABTS⁺ scavenging activity increased with freeze drying rather than hot air drying, and increased with increasing extraction temperature in both mushrooms. However, the total phenol and nitrite scavenging activity increased with hot air drying rather than freeze drying, and decreased with increasing temperature in both mushrooms. DPPH scavenging activity was not significant in both mushrooms, but decreased with increasing extraction temperature. Pearson's correlations between total flavonoid content and antioxidant activities were r=0.719~0.753 (p<0.01). As a result, the β-glucan content, total flavonoid content, and ABTS radical cation scavenging activity were highest during freeze drying and extraction at 80℃. And the highest total phenol content, DPPH radical scavenging activity and nitrite scavenging activity were obtained during hot air drying and extraction at 30℃.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.9
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• pp.4250-4256
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• 2011

Mn catalyst promoted with Cu were prepared and tested for selective catalytic reduction of $NO_x$ with $NH_3$. Performance of each catalyst was investigated for $NO_x$ activity while changing temperature, space velocity, water content and $O_2$ concentration. Hydrogen conversion efficiency of catalyst was also measured in the $H_2$-TPR system. The inhibition effect of water on catalyst was investigated with the on-off control of water supply. High activity of Mn-Cu catalyst was observed for $160{\sim}260^{\circ}C$. It is found that increase of oxygen concentration acts as a promotor to the increase of catalyst activity but water content acts as a inhibitor.

• Food Engineering Progress
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• v.15 no.3
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• pp.221-229
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• 2011

Optimization study of the hot water extraction for enhancing antioxidative activity from Auricularia auricula was performed by Taguchi approach using orthogonal matrix $L_9(3^4)$ method. The correlation between DPPH radical scavenging activity and the components of samples extracted from different extraction conditions were also analyzed. The correlation coefficient between DPPH radical scavenging activity and melanin content of A. auricula were 0.93, indicating 'good correlation'. The optimum extraction conditions was obtained at the extraction time of 1 hr. temperature of $85^{\circ}C$, solid: water ratio of 1: 40(w/v) and frequency of 2 times. Under these conditions, values of maximum DPPH free radical scavenging activity and melanin contents of A. auricula were $67.21{\pm}2.17$ and $52.94{\pm}2.10 mg/g$, respectively. Melanin content of 1.6 times and DPPH free radical scavenging effect of 130% were enhanced by optimization.