Post-Fermentation Application of Pea Protein-Based Fining Agents: Effects on Aromatic White Wine from Tămâioasa...

Pea protein is increasingly used as a plant-based alternative for fining white wines, aiming to reduce excessive polyphenols while replacing animal-derived or synthetic agents such as PVPP. This study compared pea protein alone (P), PVPP (PV), and untreated control wines (V0) with five combinations containing pea protein and additional agents, such as activated carbon (C), bentonite (B), yeast hulls (Y), and fungal chitosan (K), forming the variants PCB, PYB, PCY, PKY, and PKC applied in doses of 20 g/hL. Fining was applied to aromatic white wines of Tămâioasa Românească in triplicate (50 L tanks), obtained and followed by standard vinification steps. Main wine parameters (ethanol, malic acid, acetic acid, pH) were largely unaffected by the treatments, while free sugar levels showed only slight variations. Some significant differences were observed in total acidity. Total polyphenol content was significantly reduced by ternary fining combinations containing pea protein and yeast extract (PCY and PKY), as well as by PVPP, with reductions of approximately 37% compared to the control. Proanthocyanidins were largely preserved irrespective of the treatment, whereas flavan-3,4-diols were significantly reduced by PVPP. The fining treatments induced only small, imperceptible differences in colour, detectable solely through CIELab measurements, with the classical PVPP treatment producing wines with wines with the greenest colour tones. Volatile profiles, assessed using a GC analyser with two columns (Heracles electronic nose), were analysed in detail. Of all the 8 experimental variants, chitosan- and yeast hull-containing combinations (PKY and PCY) enhanced both varietal and fermentation-derived aromas, particularly terpenes and key esters, producing the most expressive and complex wines. In these variants, compared to control wines, eucalyptol, linalool, and trans-linalool oxide increased approximately by 13.1-23.2%, 16.7-19.3% and 341.5-428.7%, respectively. Pea protein alone preserved the aroma profile closest to the untreated control, inducing no significant differences in all the compound classes, making it a suitable alternative to PVPP. In contrast, bentonite-containing treatments reduced ester and terpene concentrations, simplifying the aroma profile and diminishing varietal characteristics. In bentonite variants, especially PCB, reduced key aroma compounds such as 2-phenylethyl acetate by 17.9%, ethyl octanoate by 12.9% and ethyl decanoate by 33.0%, linalool and trans-linalool oxide, by 18.5%, and 22.7%, respectively. These results support the use of pea protein as a selective and minimally disruptive fining agent, suitable for reducing polyphenol content while preserving wine quality. Pea protein combinations with yeast hulls, and to some extent with chitosan or other fining agents, can further enhance aroma complexity and varietal expression.