Issue link: http://winesandvines.uberflip.com/i/437909
January 2015 Wines&Vines 83 In general, high acid favors growth of yeasts early in fermentation, but most microbes (es- pecially bacteria) are not tolerant of acid. Juice pH often increases during fermentation, which favors malolactic (ML) fermentation, but pH greater than 3.6 encourages spoilage by lactic acid bacteria. Brettanomyces is more tolerant of low pH. It can tolerate a pH of 2, making it one of the few yeasts of concern to makers of Coca-Cola, which has a pH of about 2.8. Adding SO 2 inhibits the growth of spoilage bacteria and growth of wild yeasts including Brettanomyces. It also destroys thiamin and inhibits oxidation. Of course, adding cultured yeast encour- ages it to take over, but Joseph said that doesn't ensure the added yeast will finish the fermenta- tion. Other strains may prevail. Winemakers can take many steps to adjust temperature (including the use of cold soaks, tank temperature controls and pump overs) and adjust oxygen (with pump overs and rack and return, punch down, stirring or aeration and micro-oxygenation). Joseph said that cold soaks (15°-20° C) en- courage growth of non-Saccharomyces yeast early in fermentation, while cool temperatures during fermentation inhibit growth of spoilage bacteria and some yeasts. Warm temperatures can favor ML bacteria, and cool temperatures discourage spoilage organisms. She added that strict aerobic organisms like filamentous fungi and acetic acid bacteria can- not compete in low-oxygen conditions, but anaerobic and facultative anaerobes like Sac- charomyces and ML bacteria do grow. Wild and domestic yeasts Finally, Michael Silacci of Opus One described trials he conducted with yeasts isolated from various parts of the vineyard away from its winery by Anaïs Houlette-Cassou. He com- pared them to wolves (purely wild), coyotes (wild but venturing into domestic territory) and dogs (purely domestic). Attendees were offered samples of Cabernet Sauvignon inoculated with these yeasts plus a control (prise de mousse yeast) for 2013 and 2014. Subtle differences were noted, less so in the older wines. Silacci suggested that the dif- ferences tend to diminish over time. winemAking KEY POINTs UC Davis researchers discovered microbes including Brettanomyces in locations pre- sumed clean. The process for identifying strains of yeast has become quicker and cheaper in recent years. Controlling pH, temperature and oxygen level can help steer which yeast strain takes over fermentation. S T R A T E G I C D E S I G N S T U D I O A R C H I T E C T U R E B R A N D D E V E L O P M E N T A P www.STRATAap.com S T R A T A D E S I G N P L A N N I N G M A N A G E M E N T WINERY PRODUCTION HOSPITALITY ESTATES A R C H I T E C T U R E B R A N D D E V E L O P M E N T www.strataap.com S O N O M A, C A L I F O R N I A 7 0 7. 9 3 5. 7 9 4 4 Toll-Free: 877-552-4828 909-464-1373 • Fax: 909-464-1603 For your nearest dealer, contact: WIREVISE® Trellis & Fence Wire Anchor This trellis and fence wire anchor securely holds wires to end-posts. Insert the wire into and through the wirevise. It automatically locks onto the wire. No tools required. To tighten, just pull more wire through the vise. A release tool is available from AgFast for 12- 16 gauge wire. WinesVines WireVise AD.qxp_Layout 1 12/1/14 2:3 SaccharamyceS Controls EnvironmEnt in four barrEls Ethanol (%) and temperature (Cº) 24 22 20 18 16 14 12 10 8 6 4 2 0 Millions of colony-forming units Days 35 30 25 20 15 10 5 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Temperature ethanol Saccharomyces (solid lines) Non-Saccharomyces (dotted lines) non-Saccharomyces yeasts decline during fermen- tation as Saccharomyces cerevisiae grows while ethanol levels and temperatures rise. Custom made - Handcrafted Barrels WinEs & vinEs oak ConfErEnCE Feb. 1 1, 2015 napa, Calif. wvoak.com