• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.1
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• pp.76-82
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• 2008

The quality and antioxidant activity properties of Jinyangju, Korean traditional rice wine made with different additions of Citrus junos peel (0, 10, 20, 30, and 40%) were investigated. The pH and the total sugar content of the Jinyangju decreased, whereas the total acidity and alcohol content increased with greater additions of Citrus junos peel. The color L-value increased and the color a- and b-values decreased with increasing amounts of Citrus junos peel. The DPPH (1,1-diphenyl-2-picryl-hydrazyl) free radical scavenging activity increased with the addition of Citrus junos peel. The highest overall acceptability values in the sensory test for color, flavor, taste, and overall favorite were 4.2, 4.9, 5.6, 5.0, and 3.9, respectively, with the addition of 20% Citrus junos peel.

• Journal of the East Asian Society of Dietary Life
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• v.12 no.5
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• pp.388-396
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• 2002

Quality characteristics of Yukwa, Korean traditional rice cookie, added with citrus peel (2, 4 and 6%) were investigated. Yukwa was prepared by adding the water homogenate of the peel and the quality characteristics were evaluated by the expansion rate, texture, color, sensory quality and content of total carotenoid, hesperidine and naringin. The expansion rate (1,517~855%) of Yukwa with higher concentrations of citrus peel powder was lower than that of control product (1,740%) and the brittleness followed the same trend. However, the values were in the range of those of the traditional Korean Yukwa. The color of the control Yukwa (L* value: 63.3~49.9, a* value: 10.6~17.8, b* value: 12.6~56.4) was white, but with citrus peel (2~6%) light yellow~yellow (L* value. 63.3~49.9. a* value: 10.6~17.8, b* values: 12.6~56.4). Carotenoid, hesperidin and naringin contents of Yukwa with the addition of peel powder were 0.18~0.51 mg%, 36.55~101.60 mg% and 24.65~70.81 mg%, respectively. The color and the overall acceptability of yukwa with 4% of citrus peel powder were the best. This combination had some orange flavor, but no differences in both sweet and sour taste.

• Journal of Microbiology and Biotechnology
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• v.14 no.6
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• pp.1275-1279
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• 2004

Citron peel oil was extracted from citron (Citrus funas) fruit by steam distillation, and was used as starting material for microbial conversion to synthesize attractive flavor compounds by using Enterobacter agglomerans 6L. E. agglomerans was isolated from citron peel and was able to metabolize the citron peel oil and grew well ($A_{600}:\;3.0$) on the citron peel oil as the sole carbon source. Multiple terpene metabolites were produced by E. agglomerans 6L on M9 salt media with citron oil vapor. The identified bioconversion products from the citron peel oil included trans-2-decenal, octanol, $\delta$­valerolactone, $\gamma$-valerolactone, cryptone, hydroxycitronellol, cuminol, and $\gamma$-dodecalactone.

• Microbiology and Biotechnology Letters
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• v.33 no.4
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• pp.288-294
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• 2005

Flavonoid compounds show several biological activities and generally exist in the forms of glycones linking sugar moiety to main structure. Flavonoid glycones such as naringin and hesperidin in korean citrus peel are slower absorbed and consequently less active than their aglycone, naringenin and hesperetin, respectively. Therefare to increase the content of flavonoid aglycone in korean citrus peel, we used commercial carbohydrate-hydrolysing enzymes, AMG 300 L, Pectinex 100 L, and Viscozyme for transforming flavonoid glycones to aglycones. Optimal conditions of enzyme reaction were pH 5.0-7.0, $5\%$ enzyme, and 24-48 hrs. The content of naringenin and hesperetin as flavonoid aglycones in untreated citrus peel is $100\~200\;ng/g$ of dried citrus peel. In case of enzyme-treated citrus peel the content of naringenin and hesperetin increased to $1,539\∼6,674\;ng/g\;and\;1,974\∼8,906\;ng/g$ of dried citrus peel, respectively. Finally the content of flavonoid aglycones could be extracted to 10-80 times. Now enzyme-treated citrus peel may be applied to use for functional food because of its higher flavonoid aglycones as more active compounds.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.7
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• pp.993-998
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• 2011

Citrus peel powder was used to substitute 2%, 4% and 6% rice flour for making sulgidduk. Proximate composition, sensory characteristics, and principle components of sulgidduk containing citrus peel were analyzed and compared with those of sulgidduk. Protein, fat, carbohydrate, ash, color b-value (yellowness index), springiness, and adhesiveness of sulgidduk all significantly increased, whereas color L- and a-values, hardness, cohesiveness, and chewiness of sulgidduk decreased with the addition of citrus peel powder. No significant differences were observed regarding the contents of moisture and carbohydrates, or fracturability in any of the samples. Substitution of rice flour with citrus peel powder showed acceptable sourness and bitterness sensory scores, which were comparable to sulgidduk. Principle components analysis revealed total variation of 94% in the main structured information: PC1 and PC2 showed 79.31% and 14.69% variation. CP-B (citrus peel powder 4%) and CP-C (citrus peel powder 6%) associated the strongest with PC1 and sulgidduk without citrus peel powder associated with PC2. Attributes associated strongly with PC1 were color, bitterness, adhesiveness, and sourness. Therefore, sulgidduk containing CP-B can be developed based on its favorable quality characteristics and sensory evaluation.

• Journal of Applied Biological Chemistry
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• v.44 no.3
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• pp.143-146
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• 2001

Eight flavonoids, including rutin, naringin, hesperidin, quercetin, hesperetin, nobiletin, 3,5,6,7,8,3',4'-methoxylated flavone, and tangeretin, in the peels of satsuma mandarin (Citrus unshiu) species of Halla, Gungcheon, Hungjin, Namgam-20, Illnam-1, and Chungdo harvested between August and December were analyzed through HPLC. Hesperidin content of Halla harvested during early maturation was 28.70 mg/g, and was the highest among the tested citrus fruits. Rutin content of Hungjin harvested during early maturation was 2.66 mg/g. Naringin in all citrus species and hesperetin in Halla, Gungchun, Namgam-20, and Chungdo were only detected in the peel of fruits harvested during early maturation. Hesperidin and rutin were detected mainly in all citrus species, and other flavonoids in trace. Flavonoid content in the peel of fruits was high during early maturation. Flavonoid contents in the peels of all fruit samples were generally high in the early stage of maturation, which then decreased rapidly.

• Journal of Life Science
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• v.23 no.12
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• pp.1553-1556
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• 2013

Flavonoids are one of the major components found in the peels of citrus fruits. Present evidence has suggested that polymethoxyflavonoids, including nobiletin and tangeretin isolated from Citrus sunki, have many biological properties, such as anti-inflammatory, anti-oxidant, and anti-obesity capabilities. Here, we investigated the effect of Citrus sunki peel extract and its possible mechanisms on oxidative stress-induced MMP-1 expression, a major marker of skin photoaging. $H_2O_2$ induced MMP-1 expression in a dose- and time-dependent manner. Extract of Citrus sunki peel (1-25 ${\mu}g/ml$) dose-dependently decreased MMP-1 mRNA levels. When $H_2O_2$ was combined with Citrus sunki peel extract, the phosphorylation of ERK was further decreased compared to a single treatment with $H_2O_2$ alone. Moreover, U0216, an MEK inhibitor, markedly prevented the production of MMP-1. These data suggest that Citrus sunki peel extract has demonstrated protective activity against oxidative damage on MMP-1 expression, and ERK MAP kinase may be involved.

• Preventive Nutrition and Food Science
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• v.8 no.4
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• pp.349-355
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• 2003

Effects of extraction conditions, gamma-irradiation and storage conditions on bioactivities of Citrus (Citrus unshiu) peel extract were investigated. The Hunter color $L^{*}$- and $a^{*}$-values of the extract increased but $b^{*}$-value decreased with an increase in absorbed irradiation dose. DPPH radical scavenging, tyrosinase inhibition and nitrite scavenging activities were not affected by irradiation but reduced by increased storage time. Nitrite scavenging activity of the extract was the highest at pH 1.2 followed by pH 4.2 and 6.0 and not changed by storage. Results indicated that there is potential for using citrus peel byproducts as a bioactive ingredient, and that gamma irradiation brightens the color of the extract without adversely altering its biological activity.ity.

• Food Science and Preservation
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• v.11 no.3
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• pp.319-324
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• 2004

The antimicrobial activity of the extract of citrus peel prepared by the method of hot water, ethanol and sugar was examined. The results showed that the extract of citrus peel prepared by hot water or ethanol did not have antimicrobial activity, but the extract by 10$\%$(w/v) sugar revealed the high antimicrobial activity. Extracted in 10%(w/v) sugar solution for 9 days, showed the highest antimicrobial activity against 8 strains of bacteria. The minimum inhibition concentration was found to be 0.5$\%$(v/v) against S. aureus, 1.5$\%$(v/v) against B. subtilis, M. luteus and E. coli, and 2.0$\%$(v/v) against S. mutans. The antimicrobial activity of the citrus peel extract was stable regardless of the treatment at 40 $\~$ 100 $^{\circ}C$C for 20 min and unstable response to the change of pH. The results suggested the development of citrus peel as heat-stable antimicrobial agents.

• Food Science and Preservation
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• v.4 no.2
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• pp.181-187
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• 1997

New HPLC method was developed for determination of some flavonoids such as naringin, hesperidin, neohesperidin, rutin, quercitrin, naringenin, hesperetin and apigenin and their contents in citrus juice and citrus peel from citrus varieties Brown in Cheju. Detection was at 280nm and reverse phase ${\mu}$-Bondapak C-18 column was used. Water/methanol/acetic acid as the mobile phase was better than water/acetonitrile/acetic acid. Flavonoids were more stable in 20% n,n-dimethylformamide in methanol(20% DMF) than methanol and pH 12 adjusted by 1N-sodium hydroxide solution. Standard flavonoid solutions were injected three times consecutively and the reproduciability was 0.236 to 3.550%, Correlation coefficient of the calibration curve was 0.9946 to 0.9999. The exiraction efficiency of hesperidin from citrus peel was evaluated with different extraction method such as reflux, ultra-sonicating method, using three solvents (aqueous solutions with pH12 adjusted by 1N-sodium hydroxide, methanol and 20% DMF), respectively. The reflux for 4 hour in 20% DMF was the most efficient of the tested methods and solvents, and recovery percentage were 78.0∼130.0%. Flavonoids were determined in citrus juice. Naringin was 68.2mg/100$m\ell$ in Natsudaidai, Hesperidin were 85.6mg/100$m\ell$ in Sankyool and Neohesperidin was 25.3mg/100$m\ell$ in Dangyooja. Flavonoids were determined in citrus peel. Naringin was 110mg/g in Dangyooja, Hesperidin was 242mg/g in Hungjin and Neohesperidin was 87.9mg/g in Dangyooja.