Alcoholic Fermentation of Bokbunja (Rubus coreanus Miq.) Wine

In order to improve wine quality, the selection of yeast strain and of additives in the manufacture of Bokbunja (Rubus coreanus Miq.) wine was investigated. The chemical composition of the edible portions of Bokbunja fruits was 86.5% moisture, 0.2% crude protein, 0.9% crude fat, 6.6% crude fiber, 0.5% ash and $10^{\circ}Brix$ sugar, and was 2.99% fructose, 2.53% glucose and 0.07% sucrose in fruit extract. The predominant organic acids in the fruit were citric acid (14.57 mg/mL) and malic acid (2.24 mg/mL) with smaller amounts of shikimic, pyroglutamic and oxalic acid. During fermentation, citric and malic acid levels decreased, while formic and acetic acid were released. Saccharomyces cerevisiae KCCM 12224 (Sc-24) was more favorable for alcoholic fermentation of Bokbunja and the addition of 200 ppm of potassium metabisulphite to must was more efficient than other $SO_2$ sources with a higher overall acceptability score. Sc-24 increased alcohol production from 9.8 to 14.8% in a sugar concentration dependent manner $(18-28^{\circ}Brix)$. The color value of early stage Bokbunja must was improved by supplementing with Japanese apricot extract, but this did not influence the color value of Bokbunja wine after primary fermentation. The astringent taste of Bokbunja wine was reduced by removing the seed from the fruit. Sugar solution (50%, w/v) was used instead of sugar power to prevent the possibility of undissolved sugar due to insufficient mixing. This substitution did not influence sensory evaluation.

복분자 발효주의 양조특성

복분자 딸기의 일반성분은 수분 86.5%, 조단백 0.2%, 조지방 0.9%, 조섬유 6.6%, 회분 0.5%, $10^{\circ}Brix$정도의 당함량을 가지고 있었으며, 착즙액의 유리당은 fructose(2.99%), glucose(2.53%) 및 sucrose(0.07%)로 구성되어 있었다. Citric acid(14.57 mg/mL)와 malic acid(2.24 mg/mL)가 주요유기산 성분이었으며, shikimic, pyroglutamic, oxalic 순으로 미량 함유되어있었다. 본 실험에 이용된 3가지 균주중 Sc-24 균주가 복분자 발효에 적당한 것으로 판단되었으며, 발효시 오염방지를 위한 아황산 종류로는 $K_2S_2O_5$ 200 ppm 첨가가 양호하였다. Sc-24균주의 알코올 생산력은 $18-28^{\circ}Brix$의 당농도 범위에서 당농도에 비례적으로 증가하여 9.2-14.8%의 범위를 나타내었다. 매실즙의 첨가는 발효초기 복분자주 색상향상에 상당한 영향을 미치는 것으로 나타났으나 발효과정을 거치면서 색상 개선에 뚜렷한 영향을 볼 수는 없었다. 발효주의 유기산성분은 citric acid와 malic acid가 주요성분으로 발효과정에 의하여 상당량 감소되었고 formic acid와 acetic acid가 생성되었다. 씨를 포함하고 있지 않은 과즙 펄프나 과즙 상태로 발효시켰을 때 떫은맛이 약간 감소하였으며, 설탕의 용해처리는 외관상 주류의 품질에 영향을 미치지 않았다.