Optimized grape seed protein extraction for wine fining

Abstract

The extraction of proteins from grape seeds represents a promising strategy to revalorize wine industry by-products. As a natural endogenous fining agent, grape seed protein (GSE) offers an effective solution for wine clarification [1] without requiring label declaration. This study optimized the laboratory-scale GSE extraction protocol proposed by Vincenzi et al. (2013) [2] and evaluated its potential as a sustainable clarifying agent. Improvements to the protocol enhanced protein purity, partially meeting the OIV threshold of 65%, while ash content remained below 3%, within the OIV limit of 8%. Protein composition was assessed via SDS-PAGE and analyzed for total protein, total polyphenols, and polysaccharides. The potential to increase yield was explored by introducing a defatting step, which improved protein purity, though its impact on process sustainability requires further evaluation. Additionally, certain by-products during the extraction process (such as the white fraction from the initial centrifugation) were found rich in proteins and polysaccharides, suggesting potential for recovery and reuse. Reducing the water-to-solid ratio from 1:10 to 1:5 (w/v) did not significantly affect protein yield, indicating opportunities for water savings. GSE’s clarification performance was evaluated in different wine types (white, rosé, and sparkling), showing particularly strong results in white and sparkling wines. Compared to commercial fining agents (gelatin, casein, pea protein, and potato protein) GSE demonstrated comparable performance to gelatin in certain cases. Its effects on wine colour and total polyphenol retention were also assessed. In conclusion, this study highlights grape seed protein as a viable, plant-based alternative to conventional fining agents, offering efficient clarification and aligning with sustainable winemaking practices.

References

[1] Gazzola, D.; Vincenzi, S.; Marangon, M.; Pasini, G.; Curioni, A. Grape Seed Extract: The First Protein-Based Fining Agent Endogenous to Grapes. Aust J Grape Wine Res 2017, 23, 215–225, doi:10.1111/AJGW.12268.

[2] Vincenzi, S.; Dinnella, C.; Recchia, A.; Monteleone, E.; Gazzola, D.; Pasini, G.; Curioni, A. Grape Seed Proteins: A New Fining Agent for Astringency Reduction in Red Wine. Aust J Grape Wine Res 2013, 19, 153–160, doi:10.1111/AJGW.12030.