Grape seed proteins: a new fining agent for astringency reduction in red wine

Background and Aims: Protein fining agents from animal and plant sources are used to clarify and stabilize wines and to lower their astringency. Health concerns have been raised because most of the proteins used for wine fininig derive from allergenic sources. To overcome this problem, the use of a grape seed protein extract as a new fining agent for wine is proposed. Methods and Results: The procedure for extract preparation from grape seed flour, the by-product of grape oil seed industry, is described. Four grape seed protein extracts were prepared using Glycine and Sodium carbonate buffers at two different concentrations (0.05 and 0.2M, pH 10.5). The capacity of the extracts for removing potentially astringent phenols from tannin solutions and from red wines was assessed by determining the Astringency Mucin Index. The perceived astringency intensity in tannin solutions and in two red wines treated with the extracts was evaluated by sensory tests. Conclusions: Significant lowering of both Astringency Mucin Index and astringency intensity were found in treated in respect to untreated samples. Significance of the Study: Grape seed extracts appear a promising tool for wine fining agents in substitution of exogenous proteins.