Effect of Protease Combined With Heat Treatment on the Stability of Proteins in Liqueur Wine

Abstract

Background: Protein instability has been reported to be an important cause of haze in white wines; to investigate the feasibility of protease as a substitute for bentonite in the protein stability of white grape liqueurs, the effect of protease combined with heat treatment on the composition and protein stability of liqueur wines was investigated by chemical analysis, sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE), and amino acid analysis. Results: The results showed that the contents of total acid, volatile acid, pH, and glycerol were not significantly different from the blank control; the effect on total protein content and thermal stability were similar to the bentonite treatment; the L∗, b∗, and (Formula presented.) values of liqueur wines increased by 5.59%, 4.33%, and 4.33% after protease combined with heat treatment (p < 0.05); SDS-PAGE results confirmed that protease combined with heat treatment had good hydrolysis for thaumatin-like proteins (TLPs) and chitinases (CHIs) in liqueur wines. Amino acid analysis revealed that the levels of threonine, serine, tyrosine, arginine, and proline had increased, respectively, and isoleucine (1.26 mg/L) and leucine (1.16 mg/L) were newly detected after protease combined with heat treatment. Particle size analysis showed that the protease combined with heat treatment had less effect on the particle size distribution of the wines. Conclusion: Protease combined with heat treatment had a certain protein stabilizing effect and had no significant negative impact on other nutrients of liqueur wines. Thus, it can be used as an alternative to bentonite for the protein stabilization of liqueur wines.