Abstract: Based on sensory scores and viable microbial counts, we selected suitable probiotic strains of lactic acid bacteria for the fermentation of kiwifruit juice, which are tolerant to both low pH and bile salt conditions. Subsequently, the fermentation conditions were optimized and the changes in aroma composition during fermentation were detected by electronic nose. The results showed that a mixture of Lactobacillus plantarum 21805 and Lactobacillus acidophilus 20250 was used to initiate the fermentation process. The optimal fermentation conditions obtained were as follows: ratio between two probiotic strains, 1:1; inoculum size, 3%; fermentation time, 24 h; and temperature, 36 ℃. The sensory score of the fermented kiwifruit juice produced under these conditions was 81.45 points and viable cell count was 2.185 × 108 CFU/mL. The electronic nose data were analyzed by linear discriminant analysis and loadings analysis. We found that the fermented kiwi juice samples at different time points could be correctly differentiated by LDA, which confirmed the feasibility of applying electron nose to detect the flavor changes during the fermentation of kiwi juice. The flavor differences may come from terpenes, alcohols, alkanes, aromatic compounds and others. The fermented aroma started forming at 8 h of fermentation, and the key time point for producing aroma composition was at 12 h; the late stage was crucial for the flavor formation in fermented kiwifruit juice.

Key words: lactic acid bacteria, kiwifruit juice, fermentation, process optimization, aroma composition