Optimisation of polyphenol extraction from Chinese Baijiu distillers' spent grains: Stability and antioxidant capacity

Chinese Baijiu distillers' spent grains (DSGs), a major byproduct of liquor production containing valuable polyphenols, face disposal challenges because of their high moisture content and rapid spoilage. In this study, an optimised cellulase-assisted extraction process was developed for DSG polyphenols (DGPs), and their stability and antioxidant capacity were comprehensively characterised. The extraction yield of DGP was determined as the primary response variable to evaluate the effectiveness of the process. A central composite design (CCD) was employed to optimise key operational parameters: enzyme concentration, enzyme temperature and liquid-solid ratio. Results demonstrated that the optimal process conditions were a cellulase dosage of 4.0%, an enzyme temperature of 50 ºC and a liquid-solid ratio of 40 mL.g-1, obtaining a polyphenol yield of 4.20 ± 0.10 mg.g-1. Stability assessment indicated that DGP retained 68.9 ± 1.8% of the phenolic content after 7 days of frozen storage at -18 ºC, exhibiting better preservation than storage under refrigeration (47.9 ± 2.1%) and room temperature (45.5 ± 3.2%) conditions. Antioxidant assays showed concentration-dependent (0.50-8.0 µg.mL-1) scavenging capacities for ABTS (IC50 = 6.0 µg.mL-1) and DPPH (IC50 = 2.8 µg.mL-1). These findings offer valuable insights for the transformation of distillery byproducts into functional food ingredients while simultaneously addressing the challenges of solid waste management in alcoholic beverage production.