Bentonite Powder for Wine and Juice Clarification — Protein Fining, Haze Prevention, and Dosage

Introduction

A brilliant, stable glass of wine or juice owes a lot to a humble clay. Bentonite is the standard fining agent used in wineries and juice plants to remove the unstable proteins that cause haze, clarify cloudy liquid, and help produce a clean, shelf-stable product. This guide explains how bentonite fining works, why it is essential for haze stability, and how producers approach dosage through bench trials.

The Problem: Protein Haze

Grape juice and wine (and many fruit juices) contain heat-unstable proteins. Left in the finished product, these proteins can slowly unfold and clump together, especially when the bottle warms during transport or storage, forming a visible haze or deposit. Even though the haze is harmless, consumers reject cloudy wine and juice — so protein removal is a core quality step.

How Bentonite Fining Works

Bentonite is a negatively-charged clay, while the problem proteins carry a positive charge at wine/juice pH. When bentonite is dispersed into the liquid, the positively-charged proteins are electrostatically attracted to and adsorbed onto the clay surface. The bentonite-protein complexes then settle out (aided by gravity, and later by racking, filtration, or centrifugation), carrying the haze-forming proteins with them. The result is a protein-stable, clear liquid.

Because fining is a food-contact use, only a clean, food-appropriate bentonite grade should be used, and the finished process must comply with local food regulations.

Where Bentonite Fits in Winemaking

Producers use bentonite at different stages depending on their goals:

• Juice/must fining: added before or during fermentation to remove protein early and settle solids; fermentation can help mix and later resettle the clay.
• Post-fermentation fining: the most common approach for precise protein stabilisation, dosed to the level a heat-stability test says is needed.
• Juice clarification: in juice production, bentonite clarifies cloudy juice and removes proteins that would otherwise cause sediment.

Determining Dosage — The Bench Trial