Clarifying Monastrell red wine with grape seed extracts. Mechanisms of action

In winemaking, the clarification stage is crucial to reduce turbidity, so animal-derived protein clarifying agents are commonly used. Nevertheless, these can cause allergic problems and be rejected by vegans. Due to that, plant-based proteins are becoming more popular, although with limited effectiveness. This work studied the behaviour of protein-rich red and white grape seed extracts when applied to a turbid Monastrell red wine, comparing their performance and protein composition with that of different commercial clarifying agents. Results showed that egg albumin and grape seed extracts were similarly effective in reducing wine turbidity after 72 h of contact time. As regard chromatic characteristics, pea protein, white grape seed extract and isinglass significantly reduced the methylcellulose precipitable tannin content, while the anthocyanin concentration was barely affected. Proteomic studies revealed that egg albumin and grape seed extracts present a similar amino acid profile, which may explain their turbidity-reducing effectiveness, indicating that grape seed extracts could be a good alternative to both animal and plant-based clarifying agents.