Abstract: To improve the stability and quality of Huangjiu, five membranes with different molecular weight cut-offs (MWCOs; 0.2 μm, 50, 30, 10, and 1 kDa) were used to treat semi-dry and semi-sweet Huangjiu. The changes in turbidity and color difference during storage were systematically investigated, and the changes in thermal and cold stability, precipitation-prone component content, antioxidant activity, volatile flavor profile, and sensory attributes were further analyzed. In addition, the effect of pretreatment with proline-specific endoprotease or Mazyme LP protease on the stability of Huangjiu with poor stability was examined. Non-targeted metabolomic analysis was subsequently performed on the membrane-treated and enzymatically treated groups with better effects. The results indicated that reducing membrane MWCOs significantly enhanced the stability of Huangjiu. Membranes with pore size ≤ 30 kDa effectively removed high-molecular-mass substances causing turbidity, maintaining the clarity of the wine under heating-freezing conditions. However, overly fine filtration (≤ 1 kDa) impaired the antioxidant activity and led to a deterioration in the sensory quality. Comprehensive evaluation indicated that 30 kDa ultrafiltration significantly improved the clarity and stability while effectively preserving the flavor and sensory attributes of Huangjiu. Furthermore, proline-specific endoprotease effectively hydrolyzed high-molecular-mass proteins in semi-dry Huangjiu, thereby helping to inhibit precipitate formation. Metabolomic analysis further indicated that enzymatic hydrolysis significantly increased peptide abundance through protein breakdown, thereby enhancing the stability of Huangjiu, whereas ultrafiltration inhibited precipitation by physically removing macromolecular substances. This study aims to provide a scientific basis for improving the stability and quality of Huangjiu by optimizing membrane separation parameters or applying precise enzymatic hydrolysis processes and to provide research directions for future exploration of synergistic applications of membrane filtration and enzymatic hydrolysis.

Key words: Huangjiu; membrane filtration; enzymatic hydrolysis; stability; quality