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WINERY Fine-Tuning Your Wine A guide to fining agents and usage By James F. Harbertson, Ph.D., Washington State University, Prosser ine is a product of both the vineyard and the techniques the wine- maker uses. Occasion- ally, aspects of the wine need to be refined more dramatically than can be dealt with by field adjust- ments or simple blending because not every growing season or fer- mentation goes the way the wine- maker wants. Fining is used in both red and white wines to remove unwanted juice/wine components that affect clarification, astringency, color, bit- terness and aroma. The following guide will help you analyze the vari- ous problems that occur during the winemaking process and determine which fining agents are available to solve them. FINING FOR CLARIFICATION Primarily done during white-wine production, fining for clarification helps remove partially soluble com- pounds that make a wine cloudy. Clarification fining also helps speed up the settling process if added post-fermentation. Two of the most common sources of hazing that can be modified with fining are pro- teins and polysaccharides. These 80 VINEYARD & WINERY MANAGEMENT NOV - DEC 2012 problems are generally remedied post-fermentation, although pre-fer- mentation fining can help alleviate problems caused by fruit infected with mold. Bentonite is a fining agent used to remedy protein-caused hazing. Silica, aluminum and magnesium are the main components of benton- ite, but it is also associated with the cations calcium and sodium. Because bentonite's layered structure allows it to absorb water readily, it is usually added to wine or juice as a clay-water suspension. It is also common practice to hydrate bentonite and wait two days before using it. Bentonite itself has no overall charge because it is associ- ated with either sodium or calcium cations. Thus, when added to wine, the fining agent behaves much like an ion exchange system. Positively charged particles such as proteins exchange with the metal cations and the bentonite-protein complex settles to the bottom. Mixing is gen- erally required for the most efficient use of bentonite, and even after settling it can be remixed to adsorb more proteins. Proteins must have a positive charge at juice or wine pH in order to interact with bentonite. The func- tional groups on proteins that are positively charged at wine pH are amine groups such as those found in the amino acid residues lysine and arginine. Thus, it is not sur- prising that arginine and/or lysine can be depleted by bentonite fining, leading to more prolonged fermentations. Research indicates that ethanol separates the silicate layers, allow- ing larger proteins to adsorb to the bentonite. Thus, at higher concen- trations of ethanol, the protein bind- ing capacity of bentonite is improved for larger proteins that otherwise would not fit. The trend in making wine with high ethanol content is compatible with such results. Small- er proteins do not bind at greater levels with increased concentrations of ethanol. Bentonite fining done with juices prior to fermentation will not result in enhanced protein bind- ing capacity, either. AT A GLANCE Fining can help correct issues with clarity, astringency, color, bitter- ness and aroma. Deciding which fining agent to use will depend on the problem you're trying to solve. Fining with egg whites can be inconsistent due to differences in egg volume and consistency. Addressing vineyard issues such as vine nutrition and site selection can help prevent problems. WWW.VWM-ONLINE.COM