Immobilized enzymes from Geotrichum spp. improve wine quality

Higher alcohols are the byproducts of yeasts in alcohol fermentation and are harmful to human health at high concentrations. In this study, immobilized crude enzymes extracted from Geotrichum spp. strains S12 and S13 were separately employed to treat red wine, then GC and GC-MS analyses were used to determine the profiles of volatile compounds in untreated and treated wine samples. Immobilized enzymes from S13 (SA-S13E) were more active in decreasing higher alcohols than enzymes from S12. Conditions for preparing SA-S13E were optimized, and best results were obtained at a sodium alginate concentration of 35 g/L, calcium chloride of 20 g/L, and crude enzyme dosage of 3 mL. Treatment with SA-S13E significantly increased the ester content and sensory quality of wine. After being reused three times, SA-S13E still exhibited approximately 80% activity towards 1-propanol, isobutanol, and hexanol and had certain activity even after 3 months storage at -20 °C, indicating high stability in application and storage and thus showing potential in wine processing.