Spirulina (Arthrospira platensis) protein as a sustainable alternative fining agent for wine: extraction, optimization and comparative mechanistic evaluation of proanthocyanidin removal in model wine systems.

Spirulina (Arthrospira platensis) represents a promising sustainable alternative to animal-derived proteins for wine fining, though its protein extraction and proanthocyanidin (PA) removal efficiency remain poorly characterized. This study presents the first comprehensive evaluation of a purified Spirulina protein extract, designed to avoid the sensory drawbacks of whole-biomass application. A scalable bead-milling extraction process (pH 7.0, 1 M NaCl, followed by ethanol precipitation) yielded a high-purity protein isolate (63%protein) at a satisfactory recovery yield (25%). Fining (50 g/hL) in a white wine model removed 81% of PAs, comparable to patatin, pea protein, and egg albumin, but lower than gelatin (99.6%) and casein (94.0%). In a red wine model, Spirulina protein achieved higher PA removal (30%) than the other fining agents (3-19%). A matrix-dependent removal mechanism was observed, governed by protein structural flexibility in white wine and hydrogen-bond-acceptor capacity in red wine model. Spirulina protein is an effective, sustainable fining agent under model wine conditions.