Abstract:Here, the effects of pure and mixed culture fermentation by lactic acid bacteria and yeast on the total sugar, total acid, total phenol, flavonoid, and alcohol contents of jujube juice were examined. The analysis of the difference in free phenolic acids was performed with the help of Liquid Chromatography-Mass Spectrometry (LC-MS). The differences in volatile organic compounds were analyzed using Gas Chromatography-Ion Mobility Spectrometry (GC-IMS). The results showed that, regardless of pure and mixed culture fermentation, the total sugar and flavonoid contents decrease, while the total acid, total phenol, and alcohol contents increase. Furthermore, the contents of trans-ferulic acid, 4-hydroxybenzoic acid, hydrocinnamic acid, vanillic acid, benzoic acid, and syringic acid increase. Contrarily, yeast fermentation results in higher contents of total phenols, flavonoids, alcohol, phenylalanine, catechin, epicatechin, syringic acid, and sinapic acid in jujube juice but a low total acid content compared to lactic acid bacteria fermentation. The carbohydrate degradation efficiency, acid production efficiency, total phenol production rate, flavonoid retention rate, and alcohol production efficiency were higher after mixed culture fermentation. Similarly, mixed culture fermentation produces higher contents of free phenolic acids, including trans-ferulic acid, trans-cinnamic acid, vanillic acid, gallic acid, p-coumaric acid, benzoic acid, protocatechuic acid, caffeic acid, and syringic acid than does pure culture fermentation. A total of 53 volatile components were identified, including 11 alcohols, 9 esters, 8 ketones, 8 aldehydes, 2 acids, and 2 pyrazines. In mixed culture fermentation samples, flavor esters, alcohols, and aldehydes account for 17.2%, 58.2%, and 1.3%, respectively. The contents of esters and aldehydes in mixed culture fermentation samples are significantly higher than those in pure culture fermentation samples and original jujube juice samples, resulting in a strong flavor. Therefore, mixed culture fermentation using yeast and lactic acid bacteria can effectively enhance the quality and enrich the taste of fermented jujube juice. This study provides a theoretical, scientific, and practical basis for promoting the application of mixed culture fermentation in the jujube fermentation and production industry.