Abstract:Pear juice easily turns brown during processing, and lactic acid bacteria fermentation could effectively protect the color of pear juice. This study determined the changes in indices like color, polyphenol oxidase activity, contents of phenolics and ascorbic acid in pear juices during fermentation and storage, and compared with unfermented pear juice and citric acid-fortified pear juice to explore the mechanism underlying the color protection via Lactic acid bacteria fermentation for fruit and vegetable juices. During the 30-day storage, the browning index of unfermented pear juice changed from 0.073 to 0.310, which was significantly higher than that of fermented pear juice (0.134). The fermentation using Lactic acid bacteria effectively inhibited the activity of polyphenol oxidase, leading to a significantly higher retention rate (43%) for the phenolics in the fermented pear juice than that of the unfermented pear juice (16%). The stability of ascorbic acid in the fermented pear juice was higher with, the retention rate (85%) being higher than that of unfermented pear juice (50%), by which non-enzymatic browning was reduced. Lactic acid bacteria could inhibit the activity of polyphenol oxidase through producing organic acid via fermentation in pear juice, and preserve substances such as phenolics and ascorbic acid to protect effectively the color of pear juice.
