• Five methods of extracting flavonoids from jujube were compared in different aspects. • The extraction methods can significantly influence the flavonoid compositions. • DES-UAE method had outstanding ability to maintain the stability of flavonoids. • DES-UAE is an efficient and green method for extracting flavonoids from jujube.

Deep eutectic solvents (DES), recognized as tunable green solvents, show significant potential for enhancing enzyme activity in biocatalytic applications. This study investigated the effect of choline chloride–ethylene glycol DES on the lipase activity of Aspergillus niger C2J6 whole cells, employing a self-isolated endophytic strain. By varying the molar ratio (1:2–1:4) and water content (0–80%), the highest lipase activity (142.31%) was observed at a 1:1.55 molar ratio with 46% water content. The effects of changes in the composition of DES on its main physicochemical properties (including surface tension, conductivity, density, viscosity, refractive index, polarity, and water activity) were investigated to reveal the intrinsic reasons for the influence of solvents on the relative enzyme activity of lipase. Mathematical models were developed to connect DES composition with key properties. Statistical analysis revealed that among the physicochemical properties of DES, polarity exhibited the most significant impact on enzymatic activity, followed by viscosity, surface tension, and conductivity. This study provides valuable insights for designing optimized DES systems to improve biocatalytic efficiency and precision.

Co-fermentation with Saccharomyces cerevisiae and selected non-Saccharomyces yeasts is an effective approach for producing fruit wines with distinctive aromas. This study aimed to improve the aroma complexity of jujube wine by evaluating multi-strain sequential inoculation strategies. Two indigenous non-Saccharomyces strains, Hanseniaspora uvarum TD74 and Metschnikowia pulcherrima HJ79, were sequentially inoculated for fermentation in combination with S. cerevisiae. The physicochemical properties and volatile compound profiles of jujube wines produced under different inoculation conditions were analyzed using HS-SPME-GC–MS, coupled with electronic nose, electronic tongue, and chemometric analyses. Compared with single-strain fermentation, sequential inoculation with the two non-Saccharomyces yeasts produced significantly more distinct volatile profiles. In particular, the triple-strain sequential inoculation group (MHS) exhibited higher semi-quantitative levels of most ethyl esters, with a more pronounced fruity aroma in the wine, consistent with the results of sensory analysis. These findings demonstrated that the use of multiple non-Saccharomyces yeasts is an effective strategy for enhancing the aromatic diversity and overall sensory quality of jujube wine, offering a theoretical basis for the rational design of optimized starter cultures for industrial jujube wine production.