Upcycling pomegranate juice by-products into a new oenological tannin: wine color stabilization and sensory enhancement through pre-fermentation addition.

Abstract

Oenological tannins are widely used in winemaking to enhance clarification, stabilize color, modulate mouthfeel, and prevent oxidation. Among emerging sources, tannins extracted from pomegranate peel (PPE), a food industry by-product rich in ellagitannins characterized by the distinctive gallagyl group, represent a promising alternative. This study evaluated the effect of adding PPE during pre-fermentation of Sangiovese grapes, compared with commercial nutgall tannin (NGT), oak tannin (OKT), and control without tannins. Polyphenol content, antioxidant activity, and color parameters (including CIELab coordinates) were monitored throughout vinification and after six months of bottle aging, alongside sensory evaluation. PPE wines showed the highest polyphenol content (2585 mg/L) and enhanced antioxidant activity, comparable to NGT. PPE significantly increased color intensity and polymeric pigment concentration, improving long-term color stability. Bitterness was reduced and stabilized without affecting astringency or sourness. These findings highlight pomegranate tannin as an effective and sustainable oenological coadjutant, supporting circular economy approaches in winemaking.