Differences Study on the Main Nutritional Quality of Longan Vinegar before and after Fermentation

To determine the combined fermentation time of preparing longan vinegar,the changes of basic parameters of the broth fermented by yeast and acetic acid were compared. And the differences of main nutritional quality of longan vinegar before and after fermentation were analyzed. The results showed that after yeast fermentation for 48 h at 30 ℃,the total sugar in longan juice reduced to 0.4 g/100 mL and the alcohol content reached 11.5%. After acetic acid fermentation for 60 h at 30 ℃ on shallow plate,the contents of acetic acid of simultaneous fermentation group(yeast and acetic acid bacteria were inoculated at the same time and fermenting for 60 h)and moderately fermented group(acetic acid fermenting for 60 h after yeast fermenting for 24 h)reached 28.09 and 29.59 g/L. Compared with longan juice,the total phenol contents of longan vinegar produced by the two groups with better fermentation process decreased by 14.75% and 27.60%,while V_C and antioxidant capacity were significantly improved(P<0.05).The color difference analysis showed that the longan vinegar was attractive bright yellow,and the sensory evaluation results showed that the total acceptable level of the simultaneous fermentation group and moderately fermented group was high,and they had better shallow plate fermentation technology of longan vinegar.