Traditional Nuruk Research Articles

전통누룩에서 분리한 non-Saccharomyces cerevisiae의 이화학적 및 기능적 특성

This study was conducted to evaluate the alcohol-producing abilities and functional characteristics of five strains of non-Saccharomyces cerevisiae (NSC), namely, Kluyveromyces marxianus KJ-L, Wickerhamomyces anomalus KJ-1, W. anomalus CP-2, Pichia anomalus HAN-1, and Meyerozyma guilliermondii SU-L, which were isolated from Korean traditional nuruk. The selected yeast strains produced large amounts of alcohol using a carbon source of 20% glucose and were identified as NSC based on their 18S rDNA sequences. The optimal growth temperature and pH of the NSC except for M. guilliermondii SU-L were 25°C and 4.0, respectively. Two NSC strains, KJ-L and CP-2, produced 5–10% more alcohol compared to that produced by S. cerevisiae LP (SC LP) control. Although the α-amylase and ß-glucosidase activities were slightly lower in the NSC strains than in the SC LP, glucoamylase activity was 1.4-fold higher in the NSC strains than in the SC LP. The α-glucosidase inhibition activity evaluated using 1% acarbose was 29-fold higher for K. marxianus KJ-L and P. anomalus HAN-1 than that of SC LP. The five strains of NSC exhibited higher angiotensin-converting enzyme inhibitory activity with inhibition rates of 51.7–61.7% compared to that of SC LP (37.3%). The tyrosinase inhibition activities of NSC (86.4-91.5%) and SC LP (94.9%) were significantly higher than that of the positive control, kojic acid. These NSC yeast show high potential for industrial application as domestic starters for manufacturing fermented foods and cosmetics based on their physiological activities and functional characteristics.

입국과 제올라이트 사용이 고체 발효 증류주의 이취 성분 억제와 알코올 생산성에 미치는 효과

This study aimed to investigate the effect of using a combination of ipguk (koji) and zeolite, as an alternative to the traditional nuruk fermented agents and rice and rice husks combination, on off-flavor suppression in solid fermented spirits. In alcohol production from solid fermented mash, the traditional brewing combination (nuruk + rice husks) produced over 1.3 times more alcohol than that obtained using the alternative combination (ipguk + zeolite). The levels of acetic, butyric, isovaleric acids, and methyl mercaptan, the components causing the offensive odor of distilled liquor (25% alcohol), were significantly reduced upon using the alternative combination as compared to that by the traditional combination. The acetic acid level decreased from 99.38 mg/L to 19.34-24.12 mg/L when using the alternative combination. Butyric acid, isovaleric acid, and methyl mercaptan levels decreased from 95.90, 5.37, and 426.78 mg/L, respectively, to undetectable levels. The furfural content decreased up to 4.3 times. In contrast, acetaldehyde levels increased from 228.04 mg/L to 529.74-578.71 mg/L when using the alternative combination. As the moisture content of the solid-fermented mash prepared with the alternative combination increased (from 40 to 55%), the alcohol production also increased proportionally, and the alcohol content of the distillate was elevated (from 37.14 to 43.74%).

Research on the Probiotic Yeast Saccharomyces cerevisiae var. Boulardii-03 Derived from Traditional Nuruk

Research on the Probiotic Yeast <i>Saccharomyces cerevisiae</i> var. Boulardii-03 Derived from Traditional Nuruk

누룩으로부터 다양한 곰팡이의 선별과 전분 분해 활성을 이용한 동시당화발효

Various fungi were isolated from Korean traditional Nuruk and identified as ten types of fungal strains such as L. corymbifera, L. ramose, S. racemosum, R. oryzae, R. pusillus, M. racemosus, M. circinelloide, A. luchuensis, A. flavus, and A. fumigatus. Among them, four strains (A.fumigatus, A. luchuensis, A. flavus, and R. oryzae) exhibited relatively high glucoamylase activities. When the optimum reaction temperatures were verified for glucoamylase activity, A. fumigatus, A. luchuensis, and A. flavus showed the highest glucoamylase activity at 60℃, and R. oryzae showed the highest glucoamylase activity at 50℃. When simultaneous saccharification and fermentations were performed with yeast, R. oryzae showed the fastest starch degradation rate (1.17 ± 0.10 g/L·h) and the highest ethanol production (17.17 ± 1.46 g/L) for 72 hours.

누룩별 약주의 품질특성

Yakju is a traditional Korean beverage made from rice and Nuruk. In this study, the quality characteristics of Yakju by rice Nuruk and traditional Nuruk were examined. The alcohol content (%) of Yakju with A.luchuensis was 17.10-17.60, and Yakju with A.oryzae 17.40-18.00, which showed a slightly higher alcohol content (p＜0.05). The pH, amino acidity, volatile acid, and b value in Yakju with A.oryzae were significantly higher than A.luchuensis (p＜0.001). The acidity, L, a value of Yakju with A.luchuensis was significantly higher in Yakju with A.oryzae (p＜0.001). An analysis of the electronic nose of Yakju showed that the fragrance pattern of Yakju was 92.364% for the one ingredient and 7.545% for the two ingredient. The distinction by rice Nuruk was classified by the two ingredients, and when songhak was used along with traditional Nuruk, it had an aroma pattern independent of the other Yakju. According to the results of electronic tongue analysis, Yakju with A.luchuensis was found to be sour, umami, and Yakju with A.oryzae had a salty, bitter, and sweet taste. According to the sensory evaluation, taste was the most significant among the panel (p＜0.001), and the harmony of taste was the highest with Yakju with A.luchuensis. The general Nuruk and aroma patterns of Yakju are divided largely by rice Nuruk in the manufacture of Yakju. These results are expected to be great help in the development of new products for Yakju, considering the flavor and taste of Yakju.

Study of the Physicochemical Properties of Nuruk Salts Made from Different Traditional Nuruk

Study of the Physicochemical Properties of Nuruk Salts Made from Different Traditional Nuruk

전통 밀누룩에서 분리한 유산균의 특성 및 마우스 대식세포에서의 Nitric Oxide 생성에 미치는 영향

전통 밀누룩에서 분리한 유산균의 특성 및 마우스 대식세포에서의 Nitric Oxide 생성에 미치는 영향

Aspergillus oryzae을 이용한 pellet 누룩 제조 및 약주의 품질특성

Aspergillus oryzae 83-10 (AO) was inoculated in a wheat pellet with different concentrations of raw materials to produce Nuruk. The sterilized raw material (S) was found to be stable in the production of pellet-Nuruk and was suitable for the production of high enzyme power; high enzyme activity was obtained after fermentation for 32 h. The characteristics of pellet-Nuruk were investigated and the brewing characteristics were compared with those of the commercial SongHak (SH) Nuruk. The enzyme activities (dry base, unit/g) of S-AO (sterilized material and inoculated with A. oryzae) pellet-Nuruk (32 h culture) and the commercial SH Nuruk were compared. The activities of glucoamylase, α-amylase, and acidic carboxypeptidase were significantly higher in S-AO Nuruk. In terms of brewing characteristics, the soluble solid (°Brix) and total acid (%) were significantly higher in the SH mesh, and the amino acid content and alcohol content (%) were significantly higher in the S-AO mesh. The amount of Nuruk added for yakju fermentation was set at 30 unit/g × g of rice weight based on the glucoamylase activity. The enzymatic activity immediately after preparation was 26.69 unit/mL and 17.58 unit/mL for S-AO and SH, respectively. Based on these results, preparing pellet-type Nuruk should considerably save fermentation time compared with traditional Nuruk products.

재래누룩에서 분리한 N4와 N9 효모의 증류식 소주 양조특성

Soju is a Korean traditional distilled alcoholic beverage produced from mashes various crops and Nuruk which is cultured with wild microorganisms. This study was conducted to investigate rice-Soju brewing characteristics of yeasts isolated from Korean traditional Nuruk. The general components of rice (Hanarumbyeo) raw materials were 14.7 g of water, 6.8 g of crude protein, 0.9 g of crude lipid, 0.4 g of crude ash, and 76.5 g of carbohydrate in 100 g. Saccharifying and proteolytic activities in Hanarumbyeo ipguk (solid-state culture of Aspergillus luchuensis) were also determined. The alcohol content of the fermented wash from isolates was 15.37-16.58% (v/v), which is 16.7-36.0% higher than that of industrial yeasts (12.33-13.19%). Reducing sugar contents were 2.04-3.92 and 7.92-8.78 g/100 mL in the isolates and industrial yeasts, respectively. The isolated yeasts showed 25.2-52.7% higher yield of distillates (41% alcohol) compared to industrial yeasts. Forty-one components were detected in the rice distillated Soju (25% alcohol) and principal component analysis revealed differences between the isolated and industrial yeasts with respect to the contents of i-BuOH, isobutanal diethyl acetal, ethyl caprate, and tetradecanoic acid.

Characterization of brewing microorganisms isolated from Korean traditional nuruk for Cheongju production.

The objective of this study was to select and identify yeasts and molds isolated from traditional nuruk and to investigate their brewing characteristics for Cheongju production. The yeast strains Y190 (Accession ID-KACC 93251P), Y263 (Accession ID-KACC 93252P), and Y270 (Accession ID-KACC 93253P) showing high alcohol and flavor productivity were isolated and identified by phylogenetic inference based on an internal transcribed spacer 2 region sequence analysis. In addition, Aspergillus oryzae 83-10 (Accession ID-KACC 93254P) showing the highest enzyme activity was isolated. This study provides basic data for the production of Korean Cheongju and assesses the applicability of these three yeast strains and A. oryzae 83-10 isolated from traditional nuruk.

전통누룩에서 분리한 양조용 곰팡이의 혼합 배양에 따른 품질 특성

We analyzed the mixed culture characteristics of isolated brewing fungi obtained from Korean traditional nuruk for their development as fermentation starters. In a previous study, we selected appropriate fungi strains based on their large fungi bodies and strong enzyme activities. These fungi strains were mixed cultured under various combination of ratios, pHs and temperatures. As a result, total acidities of R. delemar mixed culture media were higher than those of A. oryzae cultured at 20℃ and 37℃. The pHs of A. luchuensis 34-1 and A. oryzae 37-7 as well as R. delemar 58-8 and A. oryzae 37-7 mixed culture media gradually increased with the culture period. On the contrary, total acidities of the mixed culture media gradually decreased. α-Amylase activities of R. delemar 26-4 and R. oryzae 82-7 mixed culture media were strong at 20℃ and pH 4, glucoamylase activities of R. delemar 58-8 and A. oryzae 37-7 were strong at 37℃, pH 3 and 1:2 ratio, and acidic protease activities of R. delemar 26-4 and A. oryzae 78-5 were strong at 20℃, pH 4 and 1:4 ratio. This study provides the optimal mixed culture conditions for fermentation starters based on changes in pH and total acidity, favorable enzyme activities, and fungi varieties.

Metagenomic analysis of fungal diversity in Korean traditional wheat-based fermentation starter nuruk

Nuruk, a traditional natural starter, is extensively used in the brewing of Makgeolli, one of Korea’s most popular alcoholic beverages that has been recently gaining global popularity. Thus, the quality of traditional nuruk needs to be enhanced. The nuruk mycobiome greatly influences both fermentation process as well as palatability enhancement. Limitations of culture-dependent identification restrict an accurate analysis of fungal diversity and distribution in nuruks. 454 pyrosequencing of two traditional wheat-based nuruks, prepared at two representative temperature conditions revealed a total of 153 and 53 OTUs for nuruks A and B, respectively, from a total of 33,157 ITS sequences. Phylogenetic assignments indicated that nuruk A mycobiota was dominated by the genera Aspergillus and Mucorales, whereas nuruk B by Rhizomucor. Species-level identification indicated that Mucorales sp., Aspergillus candidus, and Aspergillus cibarius predominated in nuruk A mycoflora whereas Rhizomucor pusillus, Mucorales sp., and Thermoascus crustaceus in nuruk B. The alpha diversity indices suggest nuruk A mycobiota to be more diverse than that of nuruk B at almost all time points of fermentation. Resemblances of patterns of predominant species composition and succession between culture-dependent and -independent phylogenetic analysis creates the potential to reconstruct the nuruk mycobiome in vitro, which allows the establishment of a standard inoculum for scientific comparison.

누룩추출물로 제조한 약주의 품질특성

본 연구에서는 약주의 이취와 갈변 원인물질을 알아보기 위해 제균한 누룩추출물을 첨가하여 약주를 제조하고 특성을 확인하였다. 알코올 함량은 재래누룩에서 16.33%, 개량누룩에서 18.67%로 개량누룩에서 1.1배 높게 나타났다. 산도(mL/10 mL)는 재래누룩 5.07, 개량누룩 8.32, 아미노산도 함량(mL/10 mL)도 각각 1.61, 4.72로 개량누룩이 약 2.9배 증가하였다. 당화력에 크게 영향을 미치는 글루코아밀레이스는 재래누룩에 비해 개량누룩이 3.2-44.0배 높은 활성을 보였고, 가용 고형물(r =0.965)과 색차(r =0.954)와 매우 높은 상관성을 보였다. 유기산은 숙신산과 젖산 함량이 가장 높게 나타났으며, 유리 질소화합물 함량(mg/L)은 재래누룩 540.0, 개량누룩 2285.9로 개량누룩에서 4.2배 높게 나타났다. 각 누룩추출물 약주의 이취 및 갈변은 유리질소화합물(r =0.539, 0.792)과 높은 상관성을 보였다. We investigated the fermentation characteristics of yakju made with nuruk extracts. Alcoholic fermentation was performed in an incubator set at <TEX>$25^{\circ}C$</TEX> for 14 days. The study results are as follows: the alcohol content of yakju made with modified nuruk (18.67%) was higher than that made with other nuruk extracts (14.80-17.50%). The pH value of this modified nuruk (4.13) was higher than that of traditional nuruk (3.70-4.00). The yakju containing modified nuruk showed the highest acidity (3.64 mL/10 mL), amino acidity (4.72 mL/10 mL), soluble solid (<TEX>$1.20^{\circ}Bx$</TEX>), and color difference (39.78). The concentration of organic acids in traditional nuruks was 212.25-312.97 mg/100 mL, whereas that in modified nuruk was 295.92 mg/100 mL. Nitrogen compound concentrations in modified nuruk (2285.89 mg/L) were 2-14 times higher than that in traditional nuruk. Nitrogen compound concentration and amino acidity are the physiochemical characteristics with the highest impact on off-flavor and browning of yakju. In order to reduce these unfavorable characteristics, material with a lower protein content should be used.

Exploring nuruk aroma; Identification of volatile compounds in commercial fermentation starters.

Volatile compounds of 7 commercial fermentation starters, including 4 traditional nuruk, 2 ipguk, and 1 crude amylolytic enzyme, were extracted using solvent-assisted flavor evaporation (SAFE), and extracts were analyzed using GC-MS. A total of 70 volatile compounds, including 4 esters, 10 acids, 16 alcohols, 16 hydrocarbons, 9 ketones, 5 aldehydes, 3 volatiles phenols, and 7 miscellaneous components were identified. Concentrations of volatile compounds, including 4,6-dimethylundecane, methyl 2-hydroxybenzoate, 1-hexanol, 2-phenylethanol, 3-methylbutanoic acid, and hexanoic acid were higher in 4 traditional nuruk starters than in others. The major volatile components in 2 ipguk starters were the hydrocarbones dodecane, heptadecane, octadecane, and nonadecane. Concentrations of 2-methoxy-4-vinylphenol and 3-hydroxy-2-butanone were highest in the crude amylolytic enzyme starter. Compositions and amounts of volatile compounds were different among the 7 commercial fermentation starters.

Pyrosequencing reveals bacterial diversity in Korean traditional wheat-based nuruk.

The emerging global importance of Korea's alcoholic beverages emphasizes the need for quality enhancement of nuruk, a traditional Korean cereal starter that is used extensively in traditional brewing. Apart from fungi and yeasts, bacteria known to be ubiquitously present are also a part of the nuruk ecosystem and are known to influence fermentation activity by influencing fermentation favorable factors. In the current study, bacterial diversity and temporal variations in the traditional wheat-based nuruk, fermented at two representative temperature conditions for 30 days, along with two commercial wheat-based nuruk samples for comparison analysis were evaluated using libraries of PCR amplicons and 454 pyrosequencing targeting of the hypervariable regions V1 to V3 of the 16S rRNA gene. A total of 90,836 16S reads were analyzed and assigned to a total of 314, 321, and 141 Operational Taxonomic Units (OTUs) for nuruk A, B, and C, respectively. Diversity parameters clearly indicated nuruk B to be more diverse in terms of bacterial composition than nuruk A. Taxonomic assignments indicated that nuruk A was dominated by phylum Cyanobacteria, whereas nuruk B was dominated by phylum Actinobacteria. For both nuruk A and B, members of the phylum Firmicutes mostly converged into the family Bacillaceae; these microorganisms might be present in negligible numbers at the beginning but became significant as the fermentation progressed. The commercial samples were predominated by phylum Firmicutes, which is composed of Lactobacillaceae and Leoconostocaceae. The findings of this study provide new insights into understanding the changes in bacterial community structure during traditional nuruk starter production.

온도를 달리한 누룩 발효 기간별 배양 유산균 변화 및 분리 유산균들의 효소 활성

The microbial composition in Nuruk, a Korean cereal fermentation starter, is a critical factor for the quality and organoleptic properties of traditional alcoholic beverages. This study was aimed at monitoring the compositional change and enzyme activity of culturable lactic acid bacteria (LAB) in two types of Nuruk fermented at different temperatures. All culturable LAB were isolated at various time points (0, 3, 6, 10, 20, and 30 days) and identified by 16S rRNA sequencing. In traditional Nuruk type A (TN-A), which was fermented at 36°C, the population of total culturable LAB during the fermentation period was between 104 and 105 log CFU/mL. On the other hand, the LAB population in traditional Nuruk type B (TN-B) fermented at 45°C (primary fermentation for 10 days) and 35°C (secondary fermentation for 20 days) was 102 log CFU/mL; however, these bacteria could not be detected after 6 days. Major LAB strains were identified in both Nuruk types: (1) from the MRS-culture of TN-A, Pediococcus pentosaceus at 3-30 days; (2) from MRS-culture of TN-B, P. pentosaceus at 3 days and Enterococcus hirae at 6 days. The protease activities of the dominant LAB isolated from the TN-A and TN-B cultures were within the ranges of 0.64~1.03 mg/mL and 0.74~0.81 mg/mL (tyrosine content), respectively, whereas the α-amylase activities were 0.75~0.98 mg/mL and 0.78~0.79 mg/mL (amylose content), respectively.

쌀 및 쌀 전분을 활용한 약주의 품질특성

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±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).

Characterization of Yeast for Soju (Distilled Spirits) from Korean Traditional Nuruk

본 연구에서는 국내 전통누룩에서 분리한 증류식 소주용 효모의 생리적 특성을 조사하고 동정하였다. 분리균(N4)의 26S rDNA-D1/D2 염기배열은 Saccharomyces cerevisiae 표준균주(NRRL Y-12632)와 100% 상동성을 나타내었고 다극출아에 의해서 증식하였다. Glucose, galactose, maltose, sucrose를 발효할 수 있으며 treha...

발효제를 달리하여 제조한 탁주의 휘발성 향기성분 분석

In this study, four types of Takju (rice wine) were developed using different fermentation starters; two traditional nuruk (SS and SJ), one ipguk (JE), and one crude amylolytic enzyme (HK), respectively. Sample rice wines were analyzed for ethanol, titratable acidity, pH, soluable solids, and Hunter colorimeter values. The Takju made with HK showed the highest ethanol level, while the titratable acidity of Takju made with JE was twice that of the other samples. The volatile compounds in the four types of Takju were isolated by headspace-solid phase microextraction (HSSPME) and analyzed by gas chromatography-mass spectrometry (GC-MS). A total of 49 volatile components were identified, including 27 esters, 3 acids, 10 alcohols, and 9 miscellaneous compounds. Ethyl esters and alcohols such as ethyl hexanoate, ethyl octanoate, ethyl decanoate, 2-methyl-1-pentanol, 1-pentanol, isoamyl alcohol, and 2-phenyl ethanol were the largest groups among the quantified volatiles. Although the numbers of detected volatile compounds were similar in the four types of Takju, the amount of quantified volatiles showed a great difference among samples.

Physicochemical properties of Korean rice wine (Makgeolli) fermented using yeasts isolated from Korean traditional nuruk, a starter culture

The applicability of Saccharomycopsis fibuligera CJN1020, Pichia jadinii CJN1287, and Saccharomyces cerevisiae CJN1514 isolated from Korean nuruk, a starter culture, for preparation makgeolli was investigated. These yeasts were suitable for preparation of both white rice makgeolli using a steam method and white rice-brown rice-wheat flour (WBW) makgeolli using a complex method. Upon physicochemical evaluation, there were no differences in the final ethanol concentrations between white rice makgeolli and WBW makgeolli. Differences in final ethanol yields occurred according to yeast species. Final ethanol yields using S. fibuligera and P. jadinii were 16 and 18% using S. cerevisiae. WBW makgeolli samples received higher sensory scores than white rice makgeolli for overall preference. GC/MS analysis revealed higher amounts of aromatic compounds in WBW makgeolli than in white rice makgeolli. The complex method was suitable for preparation of makgeolli using brown rice and wheat flour.