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Why are bentonite and proteins used to clarify fruit juices and wines?

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Bentonite and various proteins are used as clarifying agents in fruit juices and wines to remove suspended particles that cause cloudiness. This process, known as fining, relies primarily on the mechanisms of adsorption and chemical reaction.12

In winemaking, these agents work by adsorbing suspended materials such as yeast cells and proteins. Specifically, bentonite—a clay primarily composed of montmorillonite—is widely used to remove proteins that might otherwise precipitate or react with metals to form aggregates and clouds. Other proteins, such as gelatin, casein, and egg white, may be used for specialized purposes, including the removal of excess tannin or color. Through these interactions, fining agents help ensure the final product achieves a clear, stable appearance.234