Pre-Fermentative Addition of Sodium and Calcium Bentonites on Chardonnay Wine Changes Heat Stability, Fermentation Kinetics, Chemistry, and Volatile Composition

Protein stabilization in white wines commonly involves bentonite fining, yet the influence of bentonite type, dosage, and pre-fermentative treatment on wine composition and fermentation remains underexplored. This study assessed the effects of pre-fermentative additions of sodium and calcium bentonites at three dosage levels (24, 48, and 72 g/hL) on the fermentation kinetics, protein (heat) stability, and chemical and aromatic composition of Chardonnay wines under commercial winemaking conditions. Sodium bentonite at 72 g/hL achieved near-complete protein stabilization (ΔNTU = 3), while all calcium bentonite treatments required significantly higher cumulative dosages (up to 216 g/hL). Pre-fermentative bentonite additions led to modest reductions in primary amino nitrogen (up to 13.2 mg/L), resulting in extended alcoholic fermentation durations by up to 33 h and variable delays in malolactic fermentation across treatments. Volatile ester analysis revealed limited sensory impact, with isoamyl acetate showing the greatest reduction (up to −2.8 odor activity value; −39%) at higher bentonite levels, whereas ethyl decanoate remained largely unaffected. Overall, the pre-fermentative addition of sodium bentonite at 72 g/hL provided an effective strategy to reduce the need for post-fermentation fining while preserving key chemical and aromatic attributes of Chardonnay wine.