Wineries might use animal-derived products as finings. To remove proteins, yeast, and other organic particles which are in suspension during the making of the wine, a fining agent is added to the top of the vat. As it sinks down, the particles adhere to the agent, and are carried out of suspension. None of the fining agent remains in the finished product sold in the bottle, and not all wines are fined.
Examples of animal products used as finings are gelatin, isinglass, chitosan, casein and egg albumen. Bull’s blood is also used in some Mediterranean countries but (as a legacy of BSE (mad cow disease)) is not allowed in the U.S. or the European Union. Kosher wines use isinglass derived from fish bladders, though not from the sturgeon, since the kosher status of this fish is in debate.
Of these, casein and albumen (deriving from milk protein and egg white respectively) may be considered acceptable for lacto and ovo vegetarians respectively, but not for vegans.
As an alternative to animal products, bentonite, a clay mineral, can be used to clarify the wine. Some vintners also let the wine’s sediments settle naturally, a time-consuming process. In Australia, winemakers are required to list the use of potential allergens such as casein and albumin on the label but are not obliged to list the use of other non-vegan fining agents such as gelatin or isinglass. Some wine makers will boast on the wine label that their wine is unfiltered, because some wine connoisseurs prefer wine to be unfiltered.
For grape wines, the juice may often be contaminated with a variety of entrained, liquefied insects, arachnids and other animals. Generally, as vegans seek to minimize exploitationwherever feasible, as long as no animal-derived fining agents are used, it would be considered suitable, although interpretations may vary.