Bentonite-Clarified White Wine: Linking Clay Physico-Chemical Properties to Protein Removal Efficiency and Wine Matrix Alterations

Bentonites used for wine clarification vary widely in their ability to remove proteins and alter wine composition, yet the role of their intrinsic properties remains unclear. To address this, eight commercial bentonites with diverse physico-chemical characteristics were analyzed. The doses required for complete protein removal and stabilization were determined and then applied to clarify a Malvazija istarska (Vitis vinifera L.) white wine. Clarified wines were compared with one another and with a non-clarified control using ICP-OES for elemental composition, HPLC-DAD for phenolic compounds, and HS-SPME-GC/MS for volatile compounds. Protein removal efficiency correlated positively with Na/Ca ratio, cation exchange capacity, swelling capacity, negative ζ-potential, and internal specific surface area, and negatively with particle size and external specific surface area. Sodium and calcium showed the greatest increases in wine concentrations. Effects on individual low-molecular-weight phenols were inconsistent, though all bentonites removed a fraction of total phenols. Volatile compounds, particularly esters, were significantly reduced. When compared on a per-gram basis, bentonites that were more efficient in protein removal also showed greater removal of phenols and volatile compounds; however, at full application doses, many of these differences diminished or reversed. Overall, the study advances understanding of bentonite–wine interactions and supports more informed selection of bentonites in oenological practice.