Abstract: In order to study browning control and the pattern of change in antioxidant activity during the fermentation of apple-pear Jiaosu, we analyzed chroma, chromatic aberration, browning degree, polyphenol oxidase (PPO) activity, pH, total titratable acidity, ascorbic acid content, citric acid content, total phenolic content, total flavonoid content and antioxidant capacity. The results showed that chromatic aberration, browning degree and PPO activity initially increased and then decreased during fermentation, declining to 2.53, 0.706, 10.74 U/mL on the 140th day, while the change in L* value exhibited the opposite trend, and enzymatic browning was significantly inhibited during the late fermentation stage. pH declined gradually and then leveled off, while total titratable acidity showed the opposite trend, and ascorbic acid and citric acid contents increased first and then decreased. Total phenolic content continued to increase until reaching a maximum value of 0.426 mg/mL on the 140th day, and total flavonoid content increased overall except for a slight decline on the 50th day. Correlation analysis was used to investigate physicochemical parameters affecting browning control, including pH, total titratable acidity, and the contents of ascorbic acid, citric acid, total phenolics, and total flavonoids, which were all significantly correlated with browning degree and PPO activity (P < 0.05). During fermentation, the antioxidant activity including scavenging capacities against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical cation, hydroxyl radicaland hydrogen peroxide and reducing power increased gradually. Fermentation could inhibit enzymatic browning and improve the antioxidant activity of apple-pear Jiaosu.

Key words: apple-pear; Jiaosu; enzymatic browning; antioxidant activity