Functionalized Mesoporous Silica is a viable alternative to bentonite for wine protein stabilization

The presence of grape-derived heat unstable proteins can lead to haze formation in white wines [1], an instability prevented by removing these proteins by adding bentonite, a hydrated aluminum silicate that interacts electrostatically with wine proteins leading to their flocculation. Despite effective, using bentonite has several drawbacks as the costs associated with its use, the potential negative effects on wine quality, and its environmental impact, so that alternative solutions are needed. This project aimed at evaluating the effectiveness of functionalized mesoporous silica (FMS), in removing heat unstable proteins from white musts and wines. FMS treatments were benchmarked against a commercial Na-Bentonite in a series of experiments conducted on heat unstable white musts and wines of different origin, vintage and variety, and on different scales (from few mL to 10 hL). The stabilizing properties of the fining agents were determined by analyzing the protein profiles of treated wines (by RP-HPLC), and by assessing protein stability via heat tests [3]. In addition, the treatments’ impact on other wine parameters (e.g., organic acid profiles, metal content, macromolecules, lees formation, sensory analysis) were determined. For each wine, the dose of bentonite and FMS needed to reach full protein stability was determined by fining rate trials. The amount of FMS needed to stabilize the wines was always in line with that of bentonite, with a small variability (±10%) attributable to differences in wine composition. FMS effectively removed both thaumatin-like proteins and chitinases in a dose dependent mode, without causing other modifications on wine composition in terms of organic acid profile, ethanol content, glycerol, volatile composition, and metal content that, on the other hand, was always modified by bentonite fining that always led to an increase in Fe and Al. The analysis by triangle test of two white wines (Sauvignon blanc and Traminer) stabilized with FMS or bentonite at similar addition rates revealed the lack of significant differences (total answers = 39, p = 0. 5599 for S. blanc, p = 0.1184 for Traminer). In general, FMS showed to effectively stabilized wines at addition rates similar to those of bentonite, without causing major compositional modification, nor detectable sensory impacts, and therefore they represent a good candidate to become a viable bentonite alternative. References (max 5) 1. Van Sluyter, S.C.; McRae, J.M.; Falconer, R.J.; Smith, P.A.; Bacic, A.; Waters, E.J.; Marangon, M. Wine Protein Haze: Mechanisms of Formation and Advances in Prevention. J. Agric. Food Chem. 2015, 63, 4020–4030, doi:10.1021/acs.jafc.5b00047. 2. Lambri, M.; Dordoni, R.; Silva, A.; Faveri, D.M.D. Effect of Bentonite Fining on Odor-Active Compounds in Two Different White Wine Styles. Am. J. Enol. Vitic. 2010, 61:2, 225–233. 3. McRae, J.M.; Barricklow, V.; Pocock, K.F.; Smith, P.A. Predicting Protein Haze Formation in White Wines. Aust. J. Grape Wine Res. 2018, 24, 504–511, doi:10.1111/ajgw.12354