Effect of Co-fermentation Technology with Lactic Acid Bacteria on the Quality of Cloudy Juice of Different Varieties of Red Jujube

With a view to improving the nutritional value and the potential for deep processing of jujube, five representative varieties of jujube were selected as research materials, namely 'Hetian jujube', 'Yanchuan Goutou jujube', 'Jiaocheng jujube', 'Zanhuang jujube' and 'Ningyang jujube'. Subsequently, to explore the impact of the mixed strains fermentation on the cloudy juice quality of the various varieties of jujube, fermentation with lactic acid was carried out with the mixed strains of Lactobacillus acidophilus, Lactobacillus plantarum, and Lactobacillus fermentus. The results indicated that the juice of five jujube cultivars was a good substrate for the fermentation of mixed strains, while the number of viable bacteria at the end of fermentation was more than 6 lg CFU/mL. The fermentation of mixed strains induced the transformation of the phenolic substances and enhanced the contents of caffeic acid, protocatechuic acid, and rutin, which reached 0.67~1.13, 8.05~10.77 and 2.17~3.12 mg/mL, respectively. The antioxidant capacity of the fermented jujube juice was significantly increased, and the DPPH was increased by 38.2%~45.2%, FRAP was increased by 20.3%~60.6%. The juice of 'Hetian jujube' and 'Zanhuang jujube' were found to have higher total phenols, glucose, fructose, and malic acid, which promoted the growth of lactic acid bacteria, while their fermented juice had higher viable bacteria count, which reached 11.2 and 10.4 lg CFU/mL, respectively. Moreover, the fermented jujube juice of 'Hotan jujube' and 'Zanghuang jujube' displayed higher antioxidant capacity and sensory quality. Additionally, the fermented juices of 'Hetian jujube' and 'Zanhuang jujube' also had higher antioxidant capacity and sensory quality. The results could provide theoretical guidance for the selection and application of the fine varieties of jujube.