Bentonite is a naturally occurring absorbent clay used in winemaking, especially to stabilise white and rosé wines against protein haze. Its negatively charged surfaces attract certain positively charged proteins in wine. The bentonite-protein complexes settle out and can then be removed by racking or filtration.
Some grape proteins remain in wine after fermentation and can form a visible haze or deposit when the wine is exposed to warmth. Bentonite binds these unstable proteins and helps prevent haze from developing in the bottle. It is commonly used for white and rosé wines, although the need and amount depend on the wine’s protein stability.
Bentonite is hydrated and prepared as a slurry before being added to the wine at a measured rate. The wine is mixed sufficiently to distribute the clay, then allowed to settle. The lees and bentonite deposit are removed by racking or filtration. Winemakers generally conduct bench trials to determine the lowest effective addition, because excessive treatment can remove desirable components or reduce wine yield.
Bentonite is a mineral clay and is suitable for vegan wine production. Other fining agents include egg white, gelatin, casein and isinglass, which are animal-derived. Each agent acts differently and is selected according to the wine’s specific clarification or stability issue.
Example: a winery may use bentonite to stabilise a Sauvignon Blanc so that protein haze is less likely to develop after bottling.
Chef’s note: bentonite is a winemaking processing aid, not an ingredient added for flavour. Its use should be controlled by testing and the producer’s stability protocol.
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