Co-cultivation effects of <i>Lactobacillus plantarum</i> and <i>Pichia pastoris</i> on the key aroma components and non-volatile metabolites in fermented jujube juice

Fermented jujube products are gradually becoming popular. However, few studies have focused on the relationship between the metabolites and aroma compounds in jujube during the fermentation process. Hence, in this study, jujube was fermented with the co-culture of <i>Lactobacillus plantarum</i> and <i>Pichia pastoris</i>, and the key volatile organic components (VOCs) and non-volatile organic components (nVOCs) in the fermented jujube juice (FJJ) were studied to determine the possible aromatic production pathway during microbial metabolism and propose the possibility of regulating flavor during fermentation. Headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) was employed to analyze and compare the VOCs in the jujube juice before and after fermentation, which showed that the fermented aroma had increased floral, winy and sour notes. Specifically, 13 key aroma compounds were found using the aroma extract dilution analysis (AEDA) and aroma recombination/omission model. Additionally, 32 differential nVOC metabolites, mainly involved in amino acid and nucleotide metabolism pathways, were screened in FJJ using liquid chromatography-tandem mass spectrometry (LC-MS/MS) combined with multivariate statistical analysis. After correlation analysis, 14 nVOCs were significantly correlated with 8 key aroma compounds. This study indicates that the combination of <i>Lactobacillus plantarum</i> and <i>Pichia pastoris</i> may supply a new mixed fermentation agent towards fermented jujube products and provides reference values for flavor regulation in the co-fermentation of jujube juice.