Chitosan is an old and trusted fining agent derived from chitin, a polysaccharide found in fungi(aspergllius niger). When added to wine or beer, a mild electrostatic attraction binds yeast and other particulates to the Chitosan. This accelerates the sedimentation process (flocculation), clarifying the beverage more quickly and effectively.
Chitosan is often used in conjunction with other fining agents, especially colloidal silica products such as Kieselsol. In combination with Kieselsol, bentonite clays, gelatin, silica gel, isinglass, and other fining agents, it is used to clarify wine, mead, and beer. Added late in the brewing process, chitosan improves flocculation, and removes yeast cells, fruit particles, and other detritus that cause hazy wine. Chitosan combined with colloidal silica is becoming a popular fining agent for white wines, because chitosan does not require acidic tannins (found primarily in red wines) with which to flocculate.