Removal of specific protein components by chitin enhances protein stability in a white wine

The effect of chitin [poly(N-acetyl-1,4-ß-D-glucopyranosamine)], an abundant, low-cost natural polymer, on white wine stabilization on a laboratory scale was studied in comparison with bentonite fining. Treatments of an unfined wine with increasing doses of chitin allowed a reduction of up to 80% of the haze induced by the heat test, which corresponded to a reduction in wine protein content of less than 29%. In contrast, bentonite fining, although allowing a complete stabilization, resulted in the removal of almost all the proteins from wine. These results suggest that chitin can remove from wine protein components involved in haze formation more specifically than bentonite. SDS-PAGE analysis of both the proteins remaining in wine and those adsorbed by chitin confirmed this specificity. Chitinolytic activity detection after SDS-PAGE separation demonstrated that a main protein component removed by chitin corresponded to the class IV chitinase of grape origin involved in white wine instability. Because class IV chitinases are characterized by bearing a chitin-binding domain, a specific interaction of these wine proteins with chitin can be suggested. Preliminary trials with chitin immobilized in a column system indicated the possibility to regenerate this matrix and to use it continuously for white wine stabilization. However, the effects on both the organoleptic quality and the long-term stability of white wines treated with chitin need to be determined in the actual winemaking conditions.