Mannoproteins interfering wine astringency by modulating the reaction between phenolic fractions and protein in a model wine system

The positive effect of mannoproteins (MPs) on wine astringency is of great interest during winemaking. Phenolic components with different structural characteristics in wine could elicit different intensities of astringency when combined with salivary proteins. Aiming to use commercial MPs to modulate the unbalanced wine astringency, this work selected three commercial MPs and phenolic fractions (phenolic acids, monomeric/oligomeric procyanidins, polymeric procyanidins) with different mDP extracted from wine. The relationship between the structure and concentration of MPs, phenolic fractions, and astringency was investigated by physicochemical techniques (fluorescence quenching, SDS-PAGE, dynamic light scattering, and isothermal titration calorimetry) and sensory evaluation. Results showed that 0.6 g/L of MPs played a role in reducing wine astringency. MPs were more effective in inhibiting the interaction between monomeric/oligomeric or polymeric procyanidins and proteins than that of phenolic acids, through ternary or competitive mechanisms. Moreover, MPs with high protein portion and high molecular weight exhibited a stronger binding capacity to phenolics or protein, thus showing competing effect with phenolics for binding to protein. This work could provide the wine industry with valuable information for optimizing the application of commercial MPs to modulate wine astringency.