🍷 Bentonite

Bentonite is a clay used in winemaking as a processing aid. The OIV International Oenological Codex describes bentonites as hydrous aluminium silicates of the montmorillonite group, with exchangeable calcium, sodium or magnesium cations.

In the OIV International Code of Oenological Practices, "Treatment with bentonites" (II.3.3.5) is the addition of bentonites to wine, with the aim of preventing protein and copper hazes. The Codex says bentonites are used to clarify musts and wines or to stabilise them against unstable proteins: the bentonite binds certain unstable proteins, which can then be removed. Bentonites can also fix coloured matter.

The label of a bentonite product must state its type (natural sodium, natural calcium or activated calcium), the batch number, the optimal expiry date for activated bentonites and a warning about crystalline silica. The substances used must meet the specifications of the International Oenological Codex. For clarifying agents that only promote sedimentation, the OIV fining sheet (II.3.2.1) refers to the treatment with bentonites.