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WI ne MAKI n G What does prove handy is an overview of the parts of the process we can measure and control. I will present a model, howev- er true or false it may eventually turn out to be, that has served postmodern wine- makers well as a predictive tool. The -OH group of phenol is mildly acidic, and can be persuaded in basic solution (about pH 9) to ionize by giv- ing up its H+ , resulting in a negatively charged -O- still attached to the benzene ring. This ion is called phenolate, and it has the ability to react with oxygen to form a double bond=O called a quinone (see graphic below). Since wines are generally below 4.0 on the logarithmic pH scale, there is not much phenolate around—only about one mole- cule in 100,000. This means the reaction proceeds very slowly. Quinones absorb oxygen and bind SO2 , but that's about it. This isn't a very interesting reaction, but a special case of it is far more consequential, the subject of this article. Phenols repel water and love to ring- stack. When placed in water, they try to get away, either by evaporating (there are many phenolic aromatics common to wine—vanilla, clove, menthol and so on) or by aggregating, driven by water mol- ecules into tiny beads called colloids, herd- ed like cattle into tiny holding pens. If there are enough phenolic colloids around, the aromatic compounds will enter them and ring-stack also, diminish- ing their aromatic impact. This phenom- Phenolate Reacts with Oxygen to form a Quinone o- 2 + O2 2 enon is called "aromatic integration," and it explains why wines with good structure can contain large amounts of oak extractives, Brettanomyces-induced 4-ethyl phenol or vegetal aromatics like methoxypyrazines without deleteriously affecting the wine's aroma. Aromatic integration is a source of soul- fulness in food, be it a béarnaise, a bisque or a Bordeaux. When aromas are integrat- ed into a single voice, the food speaks to the soul the way a symphony does when the entire orchestra plays as one. o +H2 O The core reaction One type of phenolic plants find very use- ful in fruits is the vicinyl (or ortho-) diphe- nol. This is simply a phenol with two -OH groups attached to adjacent positions on the ring. This molecule has the magical ability, in reaction with oxygen, to attach itself to another phenol and recreate its original reactive diphenol structure. This odd trait allows it to react over and over, daisy-chaining to create long polymers. The browning of apples and bananas is the polymerizing of diphenols, which seal the fruit in case of injury. It was a bright feather in UC Davis's cap when Dr. Vernon Singleton in 1987 #1 Industry Website (866) 453-9701 • winesandvines.com Tanks to 4300 Gallons QUALITY WINE ALWAYS TOP PRIORITY KiLR-CHiLR™Air Systems pat pend managed white wine fermentation, storage, and stabilization Pioneers in Polyethylene for Wine 20 Years of Experience Thousands of Tanks in Use St. Regulus PMP-uNDR RedWine Fermentor pat pend managed red wine fermentation, self-pressing 208-549-1861 www.pascopoly.com Wines & Vines APRiL 2011 55