본 연구에서는 복분자 콤부차의 최적 배합비를 찾고 이화학적 특성과 항산화 활성을 알아보았다. 반응표면분석법을 통해 복분자 콤부차의 최적 배합비는 홍차 농도 10% (w/v), 복분자 농도 8.09% (w/v)로 나타났고 이 배합비로 홍차 발효 주정에 복분자 당침액과 균을 첨가하여 14일간 초산 발효와 젖산 발효 과정을 통해서 산도 4%와 pH 2.77인 콤부차를 만들 수 있었다. 복분자 콤부차의 주요 유기산은 acetic acid, lactic acid, oxalic acid로 나타났으 며 그 중에서 acetic acid가 3,705.34 mg/100 mL로 가장 높았다. 발효 후 총 폴리페놀의 함량은 763.33 μg CE/mL 로 발효 전보다 증가하였으나 콤부차 발효 후 DPPH, ABTS 라디칼 소거활성을 측정한 결과 항산화활성은 각각 46.09%, 89.81%로 발효 전보다 감소하는 것을 확인할 수 있었다. 또한 반응표면분석법을 통해 얻은 최적 배합비의 종속변수 예측값과 최적 배합비 콤부차 실험값의 산도의 평균차는 0.065, 유기산의 평균차는 0.041, ABTS 라디칼 소거활성의 평균차는 0.061이므로 예측값과 실험값은 유사 하다.

Gamma-aminobutyric acid (GABA) is a functional component with physiological activity that helps to protect the liver from blood pressure reduction and alcohol damage, and is known to be widely distributed in various vegetables and fruits. In this study, a fermented rice syrup with enhanced GABA content was developed. The improved syrup was prepared by adding monosodium glutamate (MSG) to saccharified rice and using a complex of three types of lactic acid bacteria (Lactobacillus brevis, Lactobacillus plantarum, Leuconostoc mesenteroides ) with excellent GABA production ability. The physicochemical changes of the fermented rice syrup were measured, and the final pH of the product was 4.7 with a total water-soluble solid content of 22.1 °Brix. Of the dissolved solids, glucose (39.6 mg/mL) and maltose (12.7 mg/mL) were the main components, and it was confirmed that all MSG was converted to GABA. From the experiment, it was established that the rice syrup obtained from secondary fermentation of saccharified rice is suitable as a beverage base. The fermented saccharified rice syrup was differentiated from conventional rice fermented products which typically use yeast and acetic acid bacteria in the production process. The enhanced fermented rice syrup produced in this study was made using lactic acid bacteria in the fermentation and saccharified rice.