How Fining Makes Wine Resoundingly Clear

Article from Delta Air Lines’ BusinessElite® Menu & Vinum™ guide September 2003. “Have you ever wondered how your favorite white wine gets so clear and shiny? That brilliant sheen comes from removing large particles of protein and suspended solids that can cause a wine to go cloudy in the bottle, especially when the wine is exposed to heat. The winemaker actually adds bentonite to attract proteins and clarify the wine! The term used in winemaking is fining. It’s a cool process. Bentonite is a naturally found volcanic material that is mined for commercial use around the world. It is used to clarify many liquids other than wine. Its function is rather simple. Bentonite is electrostatic, meaning that it naturally has an electric charge. Its negative charge attracts all the positively charged protons in clumps and they fall to the bottom of the vat or barrel. The wine begins to clear once the bentonite collects and ‘absorbs’ all those positively charged particles. Bentonite is very fast-acting due to its electrostatic personality. It is usually effective within 30-60 seconds, because all it is doing is attracting opposite charges. How does a winemaker know how much to use? Great question! He or she has to do trials and see which level works best. Each harvest will bring a different grape composition to the winemaker, meaning different protein levels. Different grape varieties have higher protein levels than others. If you talk to a lot of home winemakers who work with Sauvignon Blanc, they will tell you that it is a more difficult wine to clarify. Are there more proteins present than usual? On the other hand some wines can have very little protein – which means less bentonite is needed. You can ‘over-bentonite’ a wine by using too much. The result is an earthy tasting wine with a dull color – bentonite can strip color when used in large amounts. All this is another good example of how good winemaking involves many critical decisions at every step.”