Drying and fermentation process optimization of grapes pre-fermented with carbon dioxide

In order to develop a novel raisin of grapes pre-fermented with carbon dioxide, taking fresh Kyoho grape as experimental materials, and taking total phenol content and average drying rate of fermented grapes as evaluation indices, the optimal fermentation condition was presented by means of orthogonal test based on the single factor experiments. Total phenol content was determined with Folin-Ciocalteus method and average-drying-rate was detected in a hot-air drier. The results indicated that the optimized conditions were as follow: pressure at 0.14 MPa, temperature at 36℃, and fermentation time for 72 h. Under this condition, total phenol content and average-drying-rate of fermented grapes was the highest, and increased by 48.3% and 44.6%, respectively, compared with those of fresh grape. The results suggested that the raisin produced with carbonic maceration grapes was a novel product rich in phenol, and the drying-after-carbonic-maceration (DACM) was also a novel promising technology for commercial application.