Issue link: http://winesandvines.uberflip.com/i/59998
WINEMAKING knowledge that we have given up on prevention and try instead to direct the inevitable to a stable and agreeable outcome in which a microbial balance is sought rather than a draconian elimination strategy. In low-pH winemaking, we stress the role of molecular sulfur dioxide to control the growth of microorganisms. Since its effec- tiveness as an inhibitor is greatly lessened at high pH, it is more sensible to forget about molecular SO2 regulate free SO2 in this zone and instead (FSO2). of chemical oxidation of diphenols. The reaction of sulfites and peroxide is the fastest reaction known to chemistry, and it may be relied upon to prevent the formation of aldehyde from ethanol oxidation. Since SO2 Free SO2, which is substantially all bisulfite, should be main- tained to combine with H2O2 as it is formed as a side product is depleted by this action and by aldehyde binding, it must be measured by aeration/oxidation and main- tained at a reasonable level (20-30 ppm) throughout aging. A desirable consequence of sulfite oxidation to sulfuric acid is the liberation of free acidity. Over time, very high-pH wines tend to experience decreased pH and slightly increased TA. This effect can be ignored below pH 3.6 but can, during extended barrel age at pH 3.9, result in an increase of around 0.5 g/L in TA and a re- duction of 0.1 in pH. Thus wines with sufficient reactive diphenol concentration can begin aging with unbalanced acidity (e.g. pH = 3.9, TA = 4.5) and finish on target (pH = 3.85, TA = 5.0). The low-pH realm may be compared to in-town driving, where controlled navigation is paramount and little distance needs to be covered. We drive in town at 20 to 40 mph, corresponding to 3.2-3.4 pH. Maturing red wines more resemble freeway driving, in which there is less fragility and a greater imperative to traverse Sulfite-free In his scholarly tome on ancient winemaking practices, William Younger13 argued convincingly that the Romans had access to sulfites yet declined to use them in their many centuries of wine- making throughout Europe. Even before that, Georgian qvevri whites fermented on skins, stems and seeds were aged for de- cades due to their high tannin content without the formation of vinegar or aldehyde—albeit stylistically a far cry from today's light, fresh styles. Along with the millennia-long tradition of sulfite-free wines, Paul Frey argues that recent advances in our understanding of phenolic anti-oxidative capabilities, sterile filtration, liquid ni- trogen injection and other innovations in wine processing have made sulfur dioxide nonessential. Frey, Tony Norskog and others have certainly proven that viable national brands can be created and supply sound wines with reasonable reliability, clearly dem- onstrating that these wines do not require perpetual refrigeration despite Andy Waterhouse's testimony before the National Organic Standards Board to that effect last April. Andy is probably correct, however, that the production of organic wine would probably be far more widespread if sulfites were allowed. distance. The speeds with which we are comfortable on a divided highway are in the range of 55-75 mph, corresponding to pH 3.7- 3.85. I must insist here that higher pHs are irresponsible. Wines at pH 4.0 are comparable to driving at 100 mph: demonstrably unsafe regardless of conditions. Management of a positive outcome at high pH is a complex and sophisticated discussion outside the particulars of this article, but well discussed in "Winemaking at High pH."12 VintersSupply_acciai_Dec10.qxp 11/10/10 10:38 AM Page 1 20 Years Experience in Stainless Steel Manufacturing • Cross-flow Systems • Sheet Filters • Lenticular Filter Housings • Cartridge Filter Housings & Micro-filtration Plants • Lees Press Filters • Combination Filters • Pressure Leaf Filters • Tank Washers • Catwalks and Stairs VINTNERS SUPPLY COMPANY™ P.O. BOX 153 ST. HELENA, CA 94574-0153 TOLL FREE: 800-366-6809 • FAX: 707-584-7902 www.vintnerssupply.com Wines & Vines MARCH 2012 61