초록 ▼

Ⅳ. 연구개발결과
약주의 숙성기간동안 생성되는 불쾌취의 원인물질을 규명하기 위해 우선 발효제의 영향을 살펴보았다. 첫째, 재래누룩 3점, 개량누룩 1점을 활용하여 누룩 자체의 영향을 보기 위하여 누룩추출물을 제균한 후 약주를 제조하여 품질변화를 살펴본 결과, 재래누룩에 비해 개량누룩 약주의 효소활성(glucoamylase 3.2-44.0배, α-amylase 8.0배, acidic protease 5.6배)이 모두 증가하였으며,관능평가 결과 또한 이취(1.3-2.0배)와 갈변(1.8-3.0배)이 모두 증가한 것으로 나타났다.

Ⅳ. 연구개발결과
약주의 숙성기간동안 생성되는 불쾌취의 원인물질을 규명하기 위해 우선 발효제의 영향을 살펴보았다. 첫째, 재래누룩 3점, 개량누룩 1점을 활용하여 누룩 자체의 영향을 보기 위하여 누룩추출물을 제균한 후 약주를 제조하여 품질변화를 살펴본 결과, 재래누룩에 비해 개량누룩 약주의 효소활성(glucoamylase 3.2-44.0배, α-amylase 8.0배, acidic protease 5.6배)이 모두 증가하였으며,관능평가 결과 또한 이취(1.3-2.0배)와 갈변(1.8-3.0배)이 모두 증가한 것으로 나타났다. 이러한 결과에 영향을 미치는 이화학성분 중 특히 유리질소화합물과의 상관성이 이취 0.539, 갈변 0.792로 나타나 단백질이 이취 및 갈변에 가장 큰 영향을 미치는 요소임을 확인하였다. 둘째, 쌀낟알누룩의 도정율 변화에 의한 약주의 품질을 살펴본 결과, 도정도 증가에 따라 주류 갈변에 영향을 미치는 무기질(riboflavin, Fe, Mn) 및 아미노산 함량이 억제된 것을 볼 수가 있는데 백미 대비 50~70% 도정 시 riboflavin 38.5%, Fe 29.9%, Mn 28.4%, 아미노산도 20.1%, 색도37.2%가감소되었다. 셋째, 국내에서 시판되고 있는 효모 5종을 활용한 결과 와인용 효모인 퍼미빈을 첨가한 약주에서 대조효모 대비 무기질(Fe 42.5%, Mn 13.9%) 및 일반성분 함량(환원당 89.3%, 아미노산도 28.1%)의 증가가 억제된 것을 살펴볼 수 있었으며, 특히 관능평가 결과 이취가 21.9%, 갈변이 44.9% 억제되었다. 이는 퍼미빈 이용 시 완전발효로 인해 술덧에 남아있는 당 함량이 매우 적어 품질변화를 가장 적게 일으켰다고 볼 수 있다. 이로 인해 발효제로부터 유래하는 단백질 및 무기질의 영향을 감소시킴으로 약주의 이취 및 갈변이 제어될 수 있음을 알 수 있다. 넷째, 약주 숙성 시 단백질과 지방이 미치는 영향을 구체화하기 위하여 쌀 및 쌀전분을 원료로 약주의 이화학성분을 살펴본결과, 조단백질 함량이 15.69배, 조지방 함량이 2.23배 높은 쌀약주에서 아미노산도 1.13배, 색도 1.5배, 유리질소화합물 총량 1.16배가 증가하였다. 또한 단백질과 지방을 첨가한 약주의 관능평가 결과 단백질 첨가구에서 이취생성(선택율 75%)이 가장 높은 것으로 나타났으며, 이화학성분과의 상관성을 살펴본 결과 단백질은 0.98, 지방은 –0.038로 술덧의 단백질 함량이 높을수록 이취가 증가하는 것을 알 수 있다. 다섯째, 숙성약주의 불쾌취 성분을 규명하기 위해 생산된지 1달 미만의 약주와 20년 숙성된 약주의 향기성분을 살펴본 결과, 강한 자극취 성분들이 크게 증가한 것을 확인할 수 있었다. 대표적인 성분으로 isovaleraldehyde(간장향) 9.3배, isovaleric acid(치즈향) 1.12배,ethyl lactate(과일향) 7.29배, furfural(탄내) 10.26배 증가하였고, HMF(산패취), DMTS(황화합물)는 노주에서 새로 생성되었음을 확인하였다. 이러한 성분들을 노주취의 후보물질로 선정하여 각각의 성분들이 실제약주에서 어느 정도 노주취와 부합하는지 관능평가를 실시한 결과, 0.2 mg/L 첨가 시 ethyl lactate,isovaleraldehyde가, 0.5 mg/L 첨가 시 DMDS, DMTS, isovaleraldehyde가 높게 선택되어 이 성분들이 약주숙성시 불쾌취의주요성분으로작용하는것으로사료된다.
약주의 이취 및 갈변을 제어할 수 있는 공정을 설정하기 위해 첫째, 원료처리(도정율)에 따른 품질변화를 살펴보았다. 백미 기준 30% 도정 시 수분 14.1%, 회분 52.9%, 조지방 97.5%, 조단백질 18.4%의 함량은 감소하고, 탄수화물의 함량은 증가하였다. 둘째, 효소에 따른 약주의 품질특성을 살펴보기 위하여 protease 첨가 약주의 경우, 유기산총량은2.6-7.1배감소, 유리아미노산은 5.2-11.9배, 색도는 1.2-3.0배증가하였고, 발효온도는 10-30℃ 범위 중 20-25℃ 구간에서 주류의 갈변을 가장 억제 할 수 있었다. 셋째,여과방법별 약주의 아미노산도의 변화는 숙성 40일까지 prerun은 42.07%, 규조토는 47.97% 증가하였다.아미노산도의 증가는 색도의 증가와 관련되었는데, 규조토를 사용한 처리구의 색도변화가 가장 낮았고,종이여과와 prerun방법은서로 유사한것으로나타났다. 넷째, 열처리(50-80℃, 10℃간격, 30분)한누룩을 활용한 약주를 1년동안 숙성하였을 때(50℃ 기준), 비열처리 대조구에 비해 쓴맛, 자극취를 생성하는 고급알코올류(n-propanol 1.61배, isobutanol 1.22배, 2-phenyl alcohol 1.01배)와 과일향, 꽃향을 가지는 에스테르류(ethyl acetate 1.63배, ethyl laurate 1.14배, isoamyl acetate 0.33배)는증가하였고, 노주취 성분에 해당하는 furfural 0.50배, HMF 0.23배, 간장향인 isovaleraldehyde는 0.15배, 식초향인 acetic acid는 0.38배, 쓴맛을 내는 tyrosol은 0.47배 감소하였다. 색도 증가도 대조구 대비 54.87-69.40% 억제함으로써 숙성약주 제조시 생산수율 등을 고려할 때 열처리 온도 50℃, 30분이 가장 적절하였다. 다섯째 산화제(아황산염)를 100, 200, 500 mg/L 첨가했을 때, 아미노산도는 산화제에 관계없이 숙성기간에 의존적으로 증가하였고,색도는 500 mg/L 첨가구에서 가속 숙성 30일째까지 6배 이상 색도변화를 억제할 수 있었다. 아황산염 500 mg/L 첨가시 약 1년동안색변화를방지할수있으나그후는 억제가어려우므로1년단위로첨가해야 함을 알 수 있다. 여섯째, 숙성용기와 빛에 의한 약주의 품질변화를 살펴보면, UVB파 및 형광등 모두 갈색병에 저장한 약주의색도가 가장 높게 나타났으며, 빛이 없는 조건에서 가속화되고, 빛이 존재함으로써색 변화가낮아져이에대한추가적인연구가 필요하다.

Abstract ▼

As a traditional alcoholic beverage originated from Korea, rice wine has a unique aroma and color. It is made by placing nuruk on rice and only clear liquid is filtered after fermentation. Recently, many researches have been conducted to investigate and improve the characteristics of rice wine based

As a traditional alcoholic beverage originated from Korea, rice wine has a unique aroma and color. It is made by placing nuruk on rice and only clear liquid is filtered after fermentation. Recently, many researches have been conducted to investigate and improve the characteristics of rice wine based on an increase of consumption and interests related to traditional rice wine. However, in terms of quality, rice wine has been received consumer disregards since it could not be long-term aged and shipped like foreign wine or sake. As the most likely cause, the loss of original rice wine flavor or unpleasant odor generation problems from aging process have been constantly arose. Accordingly, in this research, the causative agent of unpleasant odor generation from rice wine-aging process was identified and the production method to reduce it was studied.
Above all, quality characteristics of rice wine were determined by fermentation agent. First, 3 pieces of traditional Korean nuruk and 1 piece of modified nuruk were used to see the effect of nuruk. After removing nuruk extract, the rice wine was produced. As a result of quality change analysis, all enzyme activities of rice wine from the modified nuruk were increased compared to traditional Korean nuruk (glucoamylase 3.2-44.0 times, α-amylase 8.0 times, acidic protease 5.6 times). It also has been revealed from sensory evaluation results that odor and browning were increased by 1.3-2.0 and 1.8-3.0 times, respectively. In this result, the correlations of free nitrogen-containing compounds among affecting catabolism components with odor and browning are shown to be 0.539 and 0.792, respectively, and the protein has been confirmed as a contributor with the largest effect on odor and browning. Second, analysis results of rice wine quality by the change of nuruk-rice grain milling ratio show that the amount of minerals (riboflavin, Fe, Mn) and amino acids, which influence alcohol beverage browning, is suppressed as milling ratio increases.By comparing to white rice at 50~70% milling, riboflavin was decreased by 38.5%, Fe by 29.9%, Mn by 28.4%,, level of amino acid by 20.1%,, and chromaticity by 37.2%. Third, it has been analyzed from results by using 5 kinds of commercially available yeasts that the increase of nutrients (Fe 42.5%, Mn 13.9%) and general components (reducing sugar 89.3%, amino acid degree 28.1%) was suppressed in rice wine added by wine-yeast Fermivin compared to control yeast.Moreover, the sensory evaluation results reveal that odor browning was suppressed by 21.9%, and 44.9%, respectively. When Fermivin was used, the amount of remaining sugar in rice-wine mash is very low due to the complete fermentation. Thus, the lowest quality change is produced.
Accordingly, odor and browning of rice wine can be controlled by reducing the effect of protein and minerals originated from fermentation agent. Fourth, analysis results of catabolism compounds from rice wine with rice and rice starch as raw materials in order to investigate the effect of protein and fat during rice wine aging show that the rice wine with higher amount of crude protein by 15.69 times and crude fat by 2.23 times has an increase of amino acid level by 1.13 times, chromaticity by 1.5 times, and total amount of free nitrogen-containing compound by 1.16 times. In addition, it has been found out from the sensory evaluation results of rice wine added protein and fat that the odor generation was highest in protein added group (selectivity 75%). From the analysis results of relationship with catabolism compounds, the odor was increased as the amount of protein in rice-wine mash increases, from which protein is 0.98 and fat is -0.038. Fifth, to identify unpleasant ingredients of aged rice wine, the aroma compounds analysis results of rice wine aged less than 1 month and rice wine aged for 20 years have confirmed that compounds with strong odor were highly increased. The representative compounds, which are isovaleraldehyde (soy sauce odor), isovaleric acid (cheese odor), ethyl lactate (fruit odor), and furfural (burnt odor), were increased by 9.3, 1.12 7.29, and 10.26 times, respectively. On the other hand, HMF(rancid odor) and DMTS (sulfur compounds) were newly produced from old wine. These compounds were selected as candidate materials for old rice-wine odor. The results of sensory evaluation investigating about until what extent each compound coincides with old rice-wine odor in real rice wine show that when 0.2 mg/L was added, ethyl lactate and isovaleraldehyde were chosen. Meanwhile, when 0.5 mg/L was added, DMDS, DMTS, and isovaleraldehyde were highly preferred.Hence, it is considered that these compounds act as main compounds for unpleasant odor during rice wine aging.
For determining a method to control the odor and browning of rice wine, the quality change was investigated based on raw materials processing (milling ratio). For 30%white rice milling as a standard, the amount of 14.1% moisture, 52.9% ash, 97.5% crude fat, and 18.4% crude protein was decreased, while the amount of carbohydrate is increased. Second, to analyze quality characteristics of rice wine based on enzymes, in case of rice wine added by protease, the total amount of organic acids was 2.6-7.1 times decreased, while free amino acid and chromaticity were increased by 5.2-11.9 and 1.2-3.0 times, respectively. At fermentation temperature between 20-25℃ from the range of 10-30℃, the browning of rice wine could be the most suppressed. Third, the change of amino acid according to filtration methods in rice wine, amino acids were increased by 42.07% with prerun and by 47.9% with diatomite until 40 days of aging. There is a correlation between the increase of amino acid with the increase of chromaticity. The chromaticity change by treatment using diatomite is the lowest, while the filter paper and prerun methods are appeared to be similar each other. Fourth, when rice wine from heat treated nuruk (50-80℃, 10℃ interval, 30 minutes), was aged for 1 year (standard 50℃), the higher aliphatic alcohols (n-propanol 1.61 times, isobutanol 1.22 times, 2-phenyl alcohol 1.01times), which produce bitterness and pungent odor, and the esters (ethyl acetate 1.63 times, ethyl laurate 1.14 times, isoamyl acetate 0.33 times), which have fruit and flower odor, were increased compared to non-heat treated control. The furfural corresponding with old wine odor compounds by 0.50 times, HMF by 0.23 times, soy sauce-smelled isovaleraldehyde by 0.15 times, vinegar smelled acetic acid by 0.38 times, and bitter-flavored tyrosol by 0.47 times were decreased. As the increase of chromaticity was suppressed by 54.87-69.40% compared to the control, the heat treatment at 50℃ for 30 minutes is the most appropriate by considering the production-yield rate in aged rice wine production. Fifth, when 100, 200, and 500 mg/L of oxidizing agents (sulfites) were added, the level of aminoacid was increased dependent on aging time, regardless to oxidizing agent. The chromaticity change could be suppressed to more than 6 times by 500 mg/L addition until 30 days of aging acceleration. When 500 mg/L of sulfite was added, the color change could be prevented for about 1 year and after that, suppression was difficult. Thus, it must be added by a yearly basis. Sixth, the investigation of the rice wine quality change by aging containers and light shows that the chromaticity of rice wine in a brown bottle, which are safe from both UVB waves and fluorescence light, was the highest. The color change is accelerated without light, while it was decreased in the presence of light. Regarding to this result, additional research is needed.