• Applied Biological Chemistry
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• v.38 no.3
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• pp.232-238
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• 1995

Quality changes of high fructose corn syrups (HFCS) were investigated during storage at $-5{\sim}60^{\circ}C$. Color properties such as spectrophotometric properties, HMF and Hunter color value increased continuously during storage period. And the change was most evident as storage temperature and fructose content were elevated. High fructose corn syrups all showed flow behaviors as dilatant fluid and their viscosities increased slightly during storage. Content of fructose decreased, while glucose, maltose and oligosaccharide contents increased during storage. Especially, crystallization of what was observed below $13^{\circ}C$ during storage.

• Nano
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• v.13 no.11
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• pp.1850132.1-1850132.14
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• 2018

The direct synthesis of metal-organic frameworks (MOFs) with acidic and basic active sites is challenging due to the introduction of functional groups by post-functionalization method often jeopardize the framework integrity. Herein, we report the direct synthesis of acid-base bifunctional MOFs with tuning acid-base strength. Employing modulated hydrothermal (MHT) approach, microporous MOFs named $UiO-66-NH_2$ was prepared. Through the ring-opening reaction of 1,3-propanesultone with amino group, $UiO-66-NH_2-SO_3H-type$ catalysts can be obtained. The synthesized catalysts were well characterized and their catalytic performances were evaluated in one-pot glucose to 5-HMF conversion. Results revealed the acid-base bi-functional catalyst possessed high activity and excellent stability. This work provides a general and economically viable approach for the large-scale synthesis of acid-base bi-functional MOFs for their potential use in catalysis field.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.9
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• pp.1405-1411
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• 2013

We investigated the physicochemical characteristics and antioxidant activities of Doragi (Platycodon grandiflorum) at different aging temperatures (60, 70 and $80^{\circ}C$) and for various periods of duration (5, 10, 15, 30 and 50 days). As the temperature and duration were increased, the pH of Doragi water extracts decreased from 5.22 to 4.17, whereas total acidity increased from 0.265 to 0.998 lactic acid eq.%. In addition, browning index went up from 0.092 to 1.002 and 5-hydroxymethylfurfural (HMF) content steeply rose to 50.40 mg/g from its initial zero value with an increase in temperature and duration. The radical scavenging activity of ethanol extracts was enhanced with a rise in temperature and duration as evident from the value of total polyphenol content (0.589 to 2.358 mg/g), DPPH (0.149 to 1.244 mg Trolox eq/g) and ABTS (0.354 to 1.509 mg Trolox eq/g). The correlation between physicochemical characteristics and antioxidant activities was high; the correlation between pH and total acidity showed a r value of -0.910 (P<0.01), whereas between browning index and 5-HMF content, the r value was 0.880 (P<0.01). Total polyphenol content and DPPH and ABTS radical scavenging activity were highly correlated with the r value of 0.885 (P<0.01) and 0.745 (P<0.01), respectively.

• Korean Journal of Food Science and Technology
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• v.17 no.3
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• pp.155-162
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• 1985

The sugers and free amino acids of honey(Western and Domestic honey) and the changes of diastase activity during storage at various temperatures and HMF were studied. The average content of sugers in the western honey was 40.20% of fructose, 32.43% of glucose and 1.0% of sucrose. The average ratio of fructose to glucose was 1.24. In the case of the domestic honey, average content of sugers was 37.37% of fructose, 31.92% of glucose and 0.74% of sucrose and the average ratio of fructose to glucose was 1.19. Of the 16 amino acids detected, proline was the most predominant free amino acid in all of the honey studied, representing 39.59 to 46.86% of total free amino acids. Diastase activity of honey during the storage at $50^{\circ}C$ was rapidly decreased, but it was notably changed during storage at low temperature ($4^{\circ}C$) and room temperature ($20^{\circ}C$). The accumlated content of HMF were 0.12 to 0.47mg% during storage at 80 days at $20^{\circ}C$ and 5.35 to 8.71mg% after 3 weeks storage at $50^{\circ}C$.

• Journal of Microbiology and Biotechnology
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• v.24 no.5
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• pp.667-674
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• 2014

Twenty-five Saccharomyces cerevisiae strains were screened for the highest sugar tolerance, ethanol-tolerance, ethanol production, and inhibitor resistance, and S. cerevisiae KL5 was selected as the best strain. Inhibitor cocktail (100%) was composed of 75 mM formic acid, 75 mM acetic acid, 30 mM furfural, 30 mM hydroxymethyl furfural (HMF), and 2.7 mM vanillin. The cells of strain KL5 were treated with ${\gamma}$-irradiation, and among the survivals, KL5-G2 with improved inhibitor resistance and the highest ethanol yield in the presence of inhibitor cocktail was selected. The KL5-G2 strain was adapted to inhibitor cocktail by sequential transfer of cultures to a minimal YNB medium containing increasing concentrations of inhibitor cocktail. After 10 times of adaptation, most of the isolated colonies could grow in YNB with 80% inhibitor cocktail, whereas the parental KL5 strain could not grow at all. Among the various adapted strains, the best strain (KL5-G2-A9) producing the highest ethanol yield in the presence of inhibitor cocktail was selected. In a complex YP medium containing 60% inhibitor cocktail and 5% glucose, the theoretical yield and productivity (at 48 h) of KL5-G2-A9 were 81.3% and 0.304 g/l/h, respectively, whereas those of KL5 were 20.8% and 0.072 g/l/h, respectively. KL5-G2-A9 reduced the concentrations of HMF, furfural, and vanillin in the medium in much faster rates than KL5.

• Journal of Life Science
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• v.26 no.8
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• pp.976-982
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• 2016

Seaweed has high growth rate, low land usage, high CO₂ absorption and no competition for food resources. Therefore, the use of lignin-free seaweed as a raw material is arising as a third generation biomass for bioethanol production. Various pretreatment techniques have been introduced to enhance the overall hydrolysis yield, and can be categorized into physical, chemical, biological, enzymatic or a combination. Thermal acid hydrolysis pretreatment is one of the most popular methods to attain high sugar yields from seaweed biomass for economic reasons. At thermal acid hydrolysis conditions, the 3,6-anhydro-galactose (AHG) from biomass could be converted to 5-hydroxymethylfurfural (HMF), which might inhibit the cell growth and decrease ethanol production. AHG is prone to decomposition into HMF, due to its acid-labile character, and subsequently into weak acids such as levulinic acid and formic acid. These inhibitors can retard yeast growth and reduce ethanol productivity during fermentation. Thus, the carbohydrates in seaweed require effective treatment methods to obtain a high concentration of monosaccharides and a low concentration of inhibitor HMF for ethanol fermentation. The efficiency of bioethanol production from the seaweed biomass hydrolysate is assessed by separate hydrolysis and fermentation (SHF). To improve the efficiency of the ethanol fermentation of mixed monosaccharides, the adaptation of yeast to high concentration of sugar could make simultaneous utilization of mixed monosaccharides for the production of ethanol from seaweed.

• Journal of Microbiology and Biotechnology
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• v.30 no.6
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• pp.930-936
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• 2020

The red seaweed Gracilaria verrucosa has been used for the production of bioethanol. Pretreatment for monosaccharide production was carried out with 12% (w/v) G. verrucosa slurry and 500 mM HNO₃ at 121℃ for 90 min. Enzymatic hydrolysis was performed with a mixture of commercial enzymes (Cellic C-Tec 2 and Celluclast 1.5 L; 16 U/ml) at 50℃ and 150 rpm for 48 h. G. verrucosa was composed of 66.9% carbohydrates. In this study, 61.0 g/L monosaccharides were obtained from 120.0 g dw/l G. verrucosa. The fermentation inhibitors such as hydroxymethylfurfural (HMF), levulinic acid, and formic acid were produced during pretreatment. Activated carbon was used to remove HMF. Wild-type and adaptively evolved Saccharomyces cerevisiae, Candida lusitaniae, and Kluyveromyces marxianus were used for fermentation to evaluate ethanol production.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.1
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• pp.6-13
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• 2001

The study was conducted to investigate the effect of the browning inhibitors such as PVPP(polyvinylpoly-pyrrolidone), A.A.(ascorbic acid) on nonezymatic browning factors [free sugar, total amino acid, organic acid, A.A., HMF (hydroxymethylfurfural)] and enzymatic browning factors [PRO (polyphenoloxidase) activity, polyphenol compounds] in concentrated apple juice during 90 days storage. Considering color value (L value, $\Delta$E), absorbance at 420 nm, concentrated apple juice during 90 days storage. Considering color the effect of browning inhibition. According to the storage period, the changes of nonenzymatic factors in concentrated apple juice added with browning inhibitors were similar to those in control (concentrated apple juice without browning inhibitors), which were the decreased of sucrose(0.24~0.35% at 90 days), the slight increase of glucose and fructose, the decrease of total amino acid (530.4~573.1 mg/10g at 90 days), same value of A.A. at 90 days (38.5~78.6 mg/100g), and the increase of HMF (27.8~30.6 mg/100g at 90 days). On the contrary, enzymatic browning factors were significantly inhibited in concentrated apple juice added with PVPP, judging from the slow increase of PRO activity and the significant decrease of initial value in polyphenol compounds (especially chlorogenic acid). These results suggest that PVPP plays an important role as enzymatic browning inhibitor, that is, a scavenger of polyphenol compounds by adsorption in concentrated apple juice.

• Korean Journal of Food Science and Technology
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• v.27 no.5
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• pp.729-735
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• 1995

Quality changes of starch syrups were investigated during storage at 20 and $60^{\circ}C$. Color properties such as spectrophotometric properties, HMF and Hunter color value were continuously increased during storage period. And they were largely changed as much as storage temperature and hydrolysis degree were higher. Starch syrups were all showed to flow behaviors as non-Newtonian fluids and increased slightly during storage. And monosaccharide was decreased and di- and oligosaccharide were slightly increased during storage.

• Korean Journal of Food Science and Technology
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• v.45 no.1
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• pp.34-39
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• 2013

This study was performed to investigate the antioxidant activity of mung beans with heat treatment at $130^{\circ}C$ for 2 h after acid hydrolysis. The browning index of heating after hydrolysis was 2.31 whereas heating before hydrolysis was 0.17. 5-hydromethyl-2-furaldehyde (5'-HMF) content was the highest value of 81.61 mg/g in heating after hydrolysis. The highest total polyphenol content (55.95 mg/g) occurred in heating after hydrolysis and this value was 6.4-fold higher than that of heating before hydrolysis (8.79 mg/g). 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging activity was the highest value of 22.19 mg AA eq/g sample in heating after hydrolysis whereas heating before hydrolysis was 1.75 mg AA eq/g sample.1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity was the highest value of 3.64 mg Trolox eq/g sample in heating after hydrolysis whereas heating before hydrolysis was not shown. These results suggest that heat treatment of mung beans for increasing the antioxidant activity could be effective after hydrolysis.