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Fining is a method to remove or reduce components in wine that are considered to be undesirable or excessive. Fining typically might target substances such as pigments, proteins, or tannins. The complete operation includes several procedures and depends upon chemistry (reactions) and physics (gravity). At completion, the net result of fining should leave the wine: more pleasant in appearance and/or taste; or better balanced and/or more physically stable.

Fining agents are added to the wine, but ultimately are intended to precipitate out and be removed, so they do not end up as components of wine, although trace amounts may linger. Therefore, fining agents must be heavier than both water and alcohol and not soluble in either. The majority of wines that are fined are also filtered which would remove even residual traces.

Chemical agents work by adsorbtion, forming chemical bonds with hydrogen elements in the undesired particles. Physical fining agents work by absorbtion, sucking up the tiny particles as the agent settles towards the bottom.

The process begins by selecting a fining agent appropriate to the desired purpose, relative to the substance(s) targeted for reduction or removal. Fining trials are performed to determine the correct fining agent and the least amount of which will get the desired results. The agent is then stirred into the wine to evenly distribute it for best effect which normally happens quickly. After a few hours or days, the fining agent ultimately settles to the bottom of the container (usually a tank or barrel), causing particles of the target substance(s) to precipitate out along with the agent. Afterwards, the treated wine is then separated off these settlings (lees) by siphoning (racking) and, in most cases, further clarified by filtering.

Historically used by winemakers for centuries, many common fining agents are protein-based: egg white (albumin), milk, blood, gelatin (extracted from bones and tendons), casein (from milk and cheese) and isinglass (from sturgeon bladders). Even trace amounts of some of these agents may produce mild allergic reactions in highly-sensitive people. Other agents include agars (polysaccharides), bentonite (a clay of hydrated magnesium silicates), carbons, chelators, enzymes, silicone dioxide, and synthetic polymers. Sometimes more than one fining and the use of different agents might be required to achieve the desired results.

Fining can lower high levels of tannin, remove haze, remove trace metals, and reduce color. For example, heat stabilization is a fining process intended to remove proteins that can cloud wine that might be subjected to mildly warm temperatures. Care needs to be taken to chose the proper fining agent(s) and amount to conforms to the wine style the winemaker wants to achieve. Over-fining can result in wine lacking in qualities such aroma complexity, flavor depth, viscosity, and even aging potential.

When the term "unfined" appears on a wine label, it serves as notice that the wine inside may be less than perfectly clear and probably contain more than a usual amount of tannin or sediment. That said, however, wineries are under no legal or moral obligation to reveal for what purpose or whether or not a wine has been fined and there are no legal standards or agencies to define or monitor fining.

Page created February 8, 2003; updated October 4, 2014
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