Effect of bacterial diversity on the quality of fermented apple juice during natural fermentation of Hanfu apples

The fermented cloudy apple juice (FCAJ) bacterial phase was analyzed by 16S rRNA gene-based sequencing. During fermentation, the bacterial phase transition promoted quality changes, such as carbohydrate, organic acid, total phenol, taste and volatiles of FCAJ. Citrobacter and Lactobacillus were the dominant bacterial genera of Hanfu apple juice by natural fermentation, and lactic acid was the most abundant organic acid in FCAJ. Citrobacter showed a continuous increase trend along with fermentation time, while Lactobacillus showed a slight decrease during the later period of fermentation. The contents of total phenolic and flavonoid both showed a trend of rising first and then decreasing in FCAJ during fermentation. Alcohols and esters, the main aromatic volatiles in FCAJ, showed significant increases, especially for ethanol, 3-methyl-1-butanol and ethyl acetate. Citrobacter presented a higher correlation than Lactobacillus with some volatile flavor.