🍷 Fining

Fining is the addition of an agent to juice or wine so that it binds with certain wine components and settles out. The agent reacts with wine components chemically or physically and forms a complex that separates from the wine; the lees are then removed by racking or filtration.

Fining is used to soften astringency and bitterness, to remove proteins that could cause haze, and to reduce colour by removing polymeric phenols and tannins. Bentonite helps prevent protein instability. Because the effect depends on the style of wine, agents are trialled in the laboratory first and used at the lowest effective dose, since fining can strip desirable flavours.

Common agents of animal origin are gelatine, isinglass (a fish collagen preparation), egg white, and casein and skim milk, which are milk proteins. Non-animal agents include bentonite (a clay of volcanic origin), carbon and PVPP, a synthetic polymer. EU rules list the authorised clarifying agents, among them gelatine, wheat, pea and potato protein, isinglass, casein, potassium caseinates, egg albumin, bentonite, silicon dioxide, kaolin, tannins, chitosan, yeast protein extracts and PVPP (Regulation 2019/934). Because some agents are animal-derived, labelling rules apply: in Australia, for example, casein, egg and milk used in fining must be declared on the label, while isinglass is exempt.