Valorization of tomato pomace as a source of fining agents: Effect of extraction strategy on their performance in red wine

Tomato pomace, the main by-product of tomato processing, contains proteins that can be recovered for value-added applications; however, whether different extraction strategies influence the composition and subsequent wine-fining performance of tomato pomace-derived extracts remains unexplored. In this laboratory-scale study, tomato pomace was subjected to alkaline, cellulase-assisted, phospholipase-assisted, and Alcalase-assisted extraction strategies. The extraction strategy influenced extraction yield (1.7–20.1 mg/g tomato pomace), protein content (100–485 mg/g extract), and protein recovery, which was highest for the cellulase- and phospholipase-assisted strategies (18.9 and 18.6 mg/g of the protein initially present in tomato pomace, respectively). The resulting extracts were evaluated as fining agents in Monastrell red wine. Most fining treatments reduced methylcellulose-precipitable tannins after 48 h, with the phospholipase-assisted extract producing a 15% reduction, close to the 17% obtained with commercial pea protein. The Alcalase-treated extract significantly reduced depolymerizable tannins determined by phloroglucinolysis (59–62%) and produced wines with the lowest tannin mean degree of polymerization. Tomato pomace-derived extracts produced only minor reductions in total anthocyanins (2.2–4.5%) and color intensity (3.4–5.9%), with ΔE values of 1.1–2.8, generally below the approximate threshold for visually perceptible color differences. Several treatments also reduced residual turbidity, while fining caused only limited changes in volatile composition. These findings support further investigation of tomato pomace-derived extracts as potential plant-based materials for wine fining.