• Food Science and Preservation
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• v.22 no.4
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• pp.490-497
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• 2015

This study was performed to improve the availability of reed and quality of traditional Yakju by using roasted reed. The pH of sprout Yakju was 3.43, whereas the pHs of other Yakjus were 3.57. No remarkable differences were observed in contents of total titratable acids and reducing sugars. Color changes were measured by Hunter's color value; L value decreased, whereas redness (+a) and yellowness (+b) increased during fermentation. Ethanol content of Yakjus prepared with sprout and root were 15.30% and 15.28%, respectively, which were lower than that of control Yakju (15.31%). However, there were obvious differences of ethanol contents in three types of Yakjus. The major free sugar and organic acid were glucose and lactic acid, respectively. The total polyphenol contents of sprout Yakju (4.26 mg%) and root Yakju (4.21 mg%) were much higher than that of control Yakju (2.56 mg%). The DPPH (1,1-diphenyl-2-picryl-hydrazyl) free radical scavenging activities of sprout Yakju and root Yakju were higher than those of control Yakju. Yakju prepared from 0.3% addition of sprout showed the highest score in overall preference from the sensory test.

• Food Science and Preservation
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• v.23 no.2
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• pp.204-210
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• 2016

This study aimed to find an effective preservation method of lotus leaves for the preparation of lotus-leaf Yakju throughout the year. The characteristics of Yakju containing lotus leaves pretreated by blanching, steaming, roasting, and drying were investigated in this study. The chemical properties of Yakju (pH, amino acidity, alcohol content, and volatile acid content) were significantly different for all treatments, except for the total acid content. The polyphenol content ranging from 315.89 to 462.63 ppm (p<0.05) was significantly different depending on pretreatment method L color value for Yakju was not significantly different all treatments, while a value was significantly different in Yakju containing frozen stored leaves after pretreatment. The b value was lowest for the blanching treatment, and was significantly different for all treatments. Among the organic acids present in Yakju, the oxalic, citric, and malic acid contents were significantly different for all treatments. In sensory evaluation, lotus-leaf Yakjus containing fresh leaves and dried leaves were preferred to the others in color and flavor among Yakjus prepared with lotus leaves before cold storage. However, among the Yakjus prepared with lotus leaves after cold storage, that containing blanched leaves was preferred to the others in terms of flavor, taste, and overall acceptability.

• Food Science and Preservation
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• v.19 no.6
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• pp.925-932
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• 2012

This study was performed to improve quality of traditional Yakju and compares quality of Yakju according to different rice cultivars. The pHs of Ilmi Yakju and Hanarum Yakju showed 4.14 and 4.07, respectively and the other Yakju's pHs were ranged from 3.92 to 3.98. The content of total acid of Yakju using Indica rice imported from Thailand was the highest among the samples. The major components of free sugar was glucose and the highest content of total free sugars was found in Indica Yakju. The content of reducing sugars in Yakju using Indica rice was the higher than other samples. The ethanol content of Hanarum Yakju showed higher than those Yakju's and the lowest ethanol content found for the indica Yakju. The volatile compounds from the rice Yakju were identified by GC-MS. Twenty-one volatile compounds were found in rice Yakju. And the major volatile compounds were ethanol, acetic acid, 1-methyl-1-propanol, 2-methyl-butane, 3-methyl-1-butanol, iso-amylalcohol and 1-hexanol from Yakju. As the result of sensory test, higher scores for smell and color were found for the Yakju used Hanarum Yakju. The highest score sweat and acid were found for the Anda rice Yakju in sensory test. The result of sensory evaluation indicated that Hanarum Yakju and Anda Yakju were better than the other samples, and the value of bitterness was no significant in this test.

• Food Science and Preservation
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• v.22 no.3
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• pp.353-360
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• 2015

Yakju, a Korean traditional alcoholic beverage, is made from rice and Nuruk. In this study, the fermentation characteristics of Yakju was investigated using rice and rice starch. Ingredients was classified into raw material (rice, rice starch) and starter (enzyme supplements, modified Nuruk, traditional Nuruk, and yellow rice koji) for fermentation. The crude protein content of rice, rice starch, and starter were determined as follows (%): rice 6.69, rice starch 0.44, enzyme supplements 7.84, modified Nuruk 15.29, traditional Nuruk 14.28, and yellow rice koji 7.28. The alcohol content of rice with traditional Nuruk ($20.13{\pm}0.12%$) was higher than other Yakju. The concentration of organic acids of rice starch-based Yakju (389.83~538.34 mg%) was higher than that of rice Yakju (259.27~357.70 mg%). The concentration of nitrogen compound of rice Yakju (498.38~5976.93 ppm) was higher than that of rice starch-based Yakju (600.43~4463.79 ppm). In line with these findings, further studies will be necessary for the quality analysis of the rice, rice starch and fermented starter (enzyme supplements, modified Nuruk, traditional Nuruk and yellow rice koji).

• Food Science and Preservation
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• v.15 no.4
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• pp.512-517
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• 2008

Fermentation characteristics of chestnut-added yakju prepared using various proportions of raw materials such as rice koji, rice flour, cornflour koji and cornflour were investigated. The pH of chestnut-added yakju prepared with cornflour koji and saccharified cornflour showed a higher value than that of chestnut-yakju prepared with rice koji and saccharified rice flour. The total acid content of chestnut-added yakju prepared with rice koji and saccharified rice flour was higher than that of chestnut-added yakju prepared using cornflour koji and sacharified cornflour. The reducing of sugar in chestnut-added yakju prepared with saccharified rice flour or saccharified cornflour was rapid at the first brewing stage, decreased dramatically after 2 days, and then decreased slowly after 5 days of fermentation. The value of L and a, the Hunter values, were high in chestnut-added yakju prepared with cornflour koji, and value b was high in chestnut-added yakju with rice koji. The content of iso-amyl alcohol was the highest of seven kinds of fusel oil found in chestnut-added yakju. Ethanol content increased to $17.6{\sim}18.2%$(v/v) after 8 days of fermentation. The content of lactic acid was the highest of all organic acids in the chestnut-added yakju. Sensory test results on chestnut-added yakju prepared with saccharifed corn flour showed that if rice flour is used as a sugar supplement for chestnut, the yakju prepared using koji had better flavor and taste. If cornflour was used in the preparation of chestnut-added yakju, the used of saccharified cornflour offered superior flavor and taste.

• Food Science and Preservation
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• v.21 no.4
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• pp.573-580
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• 2014

The enzymatic activity of Nuruk and the quality properties of Yakju were investigated according to different fungi. The fungi that were used in this study were Aspergillus kawachii KCCM 32819, Aspergillus niger KCCM 32005, Rhizopus japonicus KCCM 11604, Rhizopus oryzae KCCM 11272, Rhizopus oryzae KCCM 11273, Rhizopus oryzae KCCM 11276, and Mucor rouxii KCCM 60148. The study results are as follows. The saccharogenic power of Rhizopus oryzae KCCM 11272 Nuruk was the highest (3,647.72 SP/g) among all the samples. The ${\alpha}$-amylase production and protease activities were highest (3.76 DU and 4.7 tyrosine mg/min, respectively) in the Rhizopus japonicus KCCM 11604 Nuruk. The pH levels of the Yakju made with commercial Nuruk and Rhizopus japonicus KCCM 11604 Nuruk were 4.14 and 4.07, respectively. The total titratable acid content of the Yakju made with Rhizopus oryzae KCCM 11273 Nuruk was the highest (0.56%) among all the samples. Rhizopus japonicus KCCM 11604 and Rhizopus oryzae KCCM 11272 had the highest ethanol yields (15.18% and 15.10%, respectively). In the sensory evaluation carried out in this study, the panel preferred the Yakju made with Rhizopus japonicus KCCM 11604 Nuruk. Overall, however, the panel did not like the Yakju made with Aspergillus niger KCCM 32005 Nuruk.

• Korean Journal of Food Science and Technology
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• v.47 no.5
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• pp.608-614
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• 2015

Four Korean commercial rice wines of diverse sensory properties were hedonically rated by 41 consumers. Each rice wine was paired with the selection from six widely popular compatible foods such as kimchi-jjigae, dotori-muk muchim, tteok-galbi, beoseot-jeongol, satae pyeonyuk, and haemul pajeon, and consumers were asked to rate the ideal match of each pair of four rice wines and six compatible foods by using a structured, 12-cm 'just right' line scale. Hedonic ratings of wines were additionally measured after intake of the food-wine pairs. Flavor matches of rice wines with strong ginseng, medicinal, and earthy flavor (JK) or with intense grain and sweet flavor (HS) were significantly higher compared to wines with fruity (SS) or mild-balanced (BS) flavor. The preference for HS wine, which ideally matched satae pyeonyuk, increased most significantly after intake of satae pyeonyuk, while the SS wine that matched ideally with kimchi jjigae did not show any significant increase in preference after intake of kimchi jjigae. Matching wines with food does not negatively affect the preference for the wine; rather, intake of a wine-food pairing increases the overall preference for rice wine.

• Food Science and Preservation
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• v.30 no.1
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• pp.155-169
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• 2023

Jerusalem artichoke (JA, Helianthus tuberosus L.) has a great potential to enhance the quality of yakju due to the plentiful inulin content which is functional and indigestible carbohydrate in human. In this study, the optimal preparation conditions such as the added amount and steam treatment of JA were investigated to improve the quality of yakju. As the amount of JA added to yakju increased, alcohol production decreased, whereas fermentation was performed well when the steam-cooked JA was added to yakju. The pH and total acidity of yakju decreased and increased, respectively, when the amount of JA added to yakju increased, whereas pH and total acidity of yakju increased and decreased, respectively, when the steam-cooked JA was added to yakju. The free sugar and organic acid contents of yakju increased and decreased, respectively, when the amount of JA added to yakju increased, whereas those of yakju decreased when the steam-cooked JA was added to Yakju. Amino acid content of JA decreased as the amount of JA added to yakju increased and that of JA significantly decreased when the steam-cooked JA was added to yakju. In the sensory evaluation analysis, the addition of 10% unsteam-cooked JA to yakju was the best when considering sweetness, flavor, sourness, and overall preference of yakju supplemented with JA. Consequently, utilizing JA to yakju may contribute to the improvement of the quality of yakju.

• Food Science and Preservation
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• v.20 no.3
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• pp.365-371
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• 2013

The organic acids, fuel oil contents and antioxidant activities of Yakju with the addition of rice varieties were investigated. The rice cultivars that were used in this study were Ilmi rice, Hopyung rice, Hopum rice, Hanarum rice, Anda rice and Indica rice. The study results are as follows: the pH values of Ilmi Yakju and Hanarum Yakju were 4.14 and 4.07, respectively, and those of the other Yakjus, 3.92~3.98. The total titratable acid content of the Yakju for which Indica rice was imported from Thailand was highest among the samples. The reducing sugars content of the Yakju for which Indica rice was used was higher than that of the other samples. The ethanol content of the Hanarum Yakju was higher than that of the other Yakjus, and the lowest ethanol content was found for the Indica Yakju. The major organic acid component of the Yakju was lactic acid. The total organic acid content was highest in the Indica rice Yakju. The amounts of the following main fusel oils were highest, in the following order: 2-butyl alcohol, 2-pentanol, N-propyl alcohol, acetaldehyde, ethyl acetate, methyl alcohol and 2-methyl-1-propyl alcohol. The DPPH free radical scavenging activity of the Indica rice Yakju was much higher than that of the Ilmi rice Yakju and the Hanarum rice Yakju. Also, the SOD activity of the Indica rice Yakju was strongest among all the samples. The total polyphenol content of the Indica rice Yakju was the highest among all the samples.

• Food Science and Preservation
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• v.17 no.1
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• pp.36-41
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• 2010

Fermentation characteristics of yakju prepared with addition of Opuntia ficus indica were examined, with respect to the nature and concentration of additional added materials. The pH level began to decrease after the secondary brewing stage and the total acid content increased during fermentation. The level of reducing sugars in yakju prepared with Opuntia ficus indica increased at the first brewing stage and then slowly decreased after 4 days of fermentation. The ethanol content of supplemented yakju rapidly increased during the initial 6 days of fermentation, to a maximum content of 17.1% after 14 days. The free sugar content was higher in yakju fermented with Opuntia ficus indica stem compared with fruit. The level of organic acids increased as the amount of Opuntia ficus indica material increased. Organic acid level increased during fermentation and lactic acid was the main organic acid in yakju fermented with Opuntia ficus indica. Sixteen volatile compounds were found by GC-MS in supplemented yakju. The most prominent volatile component was iso-amyl alcohol, followed by butyl alcohol and methyl esters. The DPPH radical-scavenging activity of yakju fermented with Opuntia ficus indica stem was higher than when yakju was prepared with fruit. Sensory scores of yakju fermented with 20% (w/v) fruit and 10% (w/v) stem were greater than those of yakju prepared by other treatments.