Abstract:In this study, strawberry was used as raw material to ferment into jiaosu. The total sugar, total titratable acidity, citric acid, L-malic acid, acetic acid, lactic acid, total phenols and antioxidant properties (scavenging activities against DPPH radical, hydroxyl radical, ABTS radical and reducing power) were investigated. The relationship between metabolites and the antioxidant indicators was studied. Besides, principal component analysis was used to establish the change of comprehensive index in the fermentation process of strawberry jiaosu. The results showed that during the initial fermentation time (the first 20 days), the content of total sugar decreased little, and the content of total phenolic, total titratable acidity, citric acid and L-malic acid decreased. The scavenging ability of strawberry jiaosu against DPPH free radical and ABTS free radical was low, and the reducing power was less than 0.5. Meanwhile, the promoting effects against the hydroxyl radical was observed. In the mid-fermentation (20 d to 30 d), the content of total sugar decreased obviously, and the content of total titratable acidity, citric acid, L-malic acid, acetic acid and lactic acid and total phenols increased obviously, with scavenging activities against DPPH radical, hydroxyl radical, ABTS radical and reducing power increasing significantly. During the later phase of fermentation (30 d to 75 d), the content of each metabolites tended to be stable, and the content of citric acid and L-malic acid decreased slightly. The reducing power of strawberry jiaosu increased in the entire fermentation process, and the reduction rate against reducing power slowed down. After fermentation of 30 d, the total sugar, total titratable acidity, organic acids, total phenolic and antioxidant activity tends to be stable. The comprehensive evaluation index(CEI) of strawberry jiasu has the highest comprehensive score at 75 d, which can be used as the reference end point of fermentation or the basis of adding syrup or yeast. The establishment of comprehensive indexes in the fermentation process of strawberry jiaosu provides a theoretical basis for the precise fermentation of strawberry jiaosu.