Impact of yeast intracellular and extracellular mannoproteins on the hydrolysis of the esters during wine accelerated aging

Fruity esters are crucial volatile compounds for wine aroma stability1,2. Building on evidence that spent yeast polysaccharides could impact the stability of these esters2, this study explores the role of mannoproteins (MPs) in preserving ester stability during wine storage. Commercial (CMPs) and purified from synthetic grape juice fermentation (WMPs) mannoproteins were characterized using UV spectrophotometry, electrophoresis, and high-performance liquid chromatography. Results showed that the content of proteins bound to polysaccharides and that of low MW polysaccharides (1.0~40 kDa) was higher in CMPs than in WMPs. To assess the impact of CMPs and WMPs on ester hydrolysis, these were added to model wine (spiked with 6 esters) and real white wines at different concentrations. Ester concentrations were measured by liquid-liquid extraction and GC-MS during accelerated aging at 50°C. After one month, all esters in model wine greatly decreased (64-92% reductions). The addition of 400 mg/L CMPs slightly delayed the hydrolysis of the six esters, while WMPs showed almost no effect. Results indicated that CMPs, that are the MPs with higher bound protein concentration and low MW polysaccharide contents, were the products able to delay the decrease in esters concentration, likely by interacting with fruity esters thus reducing their hydrolysis during aging.