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WINEMAKING ary fermentation process and the time and labor to care for those fermentations. Dealing with sluggish or stuck fermenta- tions and fermentations that are going badly requires extra work. The low populations of wild yeast com- ing in on the grapes take time to multiply. Finally, S. cerevisiae eventually will multiply to sufficient numbers and go on to complete the fermentation. Wild secondary fermenta- tion can coincide with primary fermenta- tion or start at the end of primary and be very slow. The rate of fermentation for both depends on fermentation conditions such as nutrients, temperature, pH, population and SO2 . Wild primary and secondary fermenta- smell), which can be corrected if caught early in the fermentation. tions can take months to complete, and each year is different. Larger wineries need to turn over tanks and/or barrels to accommodate the volume of wine produced, and most often they use a controlled fermentation using pure cultured S. cerevisiae yeast, of which some strains will begin to ferment within hours. These in- oculated fermentations can proceed quickly, with completion within a week or two. Following primary fermentation the wine is inoculated with Oenococcus oeni to complete secondary fermentation within weeks. Wild fermentation can go bad in a very short time. Low Saccharomyces population in the wild mix may result in a stuck fermen- tation once the alcohol level is high enough to eliminate alcohol-sensitive wild yeast. Wild yeasts are nutrient-sensitive, and if the nutritional requirements are depleted or not being met, the yeast population will fail. A stuck fermentation can be difficult to restart, and in some cases it may require the addition of cultured Saccharomyces yeast to kick-start it and allow the fermentation to complete. The real trick is to get the fermentation going quickly before other microbes jump in to take over while the protective barrier of carbon dioxide produced during fermenta- tion drops. Prior to the advent of modern winemaking methods, the annual losses of wine due to failed wild fermentations were commonly 20% or more. Dr. Peter Salamone, North American technical manager for wine- making supplier Laffort USA, said, "One man's diversity is another man's spoilage." Unfermented sugars and the lack of compet- ing viable yeasts encourage Lactobacillus (LAB) and Acetobacter growth. In stuck fermentations, Acetobacter aceti (which pro- duces acetic acid, or vinegar) can soar if not detected early. Nutrient-deficient fermenta- tions, LAB and some yeasts can produce high levels of hydrogen sulfide H2 S (rotten egg Smelling for ethyl acetate and H2 W S inemaker Antoine Favero of Mazzocco Winery has been using wild fermenta- tions for 15 years. Being very conscientious both in and out of the vineyard, Favero counts an "incredibly low" number of stuck fermentations and says he has never lost a fermentation. He makes SO2 additions at the crusher and post- secondary fermentation. "During native fermentations, I'm typically looking for an evolution of aromas," he said, adding that it's OK to smell ethyl acetate for the first two or three days. "However, if the ethyl acetate does not disappear by the end of the third day, replaced by fruity aromatics, then I may do an intervention in the form of yeast addition." Favero said he does not encourage co-fermentations—especially with Zinfandel. Sometimes the secondary fermentations go native, but he said there are years when he doesn't inoculate. Leo Hansen of Stuhlmuller Vineyards checks daily for off odors—"mainly H2 S if a lot needs aeration or potential lack of nutrients." Any suspicious fermentation is sampled and sent to the lab for analysis. J.J. CONCRETE FERMENTATION TANKS NEW 2,200 GALLON TANKS THIS SEASON! VISIT US AT tanksinconcrete.com TO SEE WHAT WINEMAKERS ARE SAYING ABOUT OUR CONCRETE FERMENTORS OR CALL 888.807.4575 Wines & Vines APRiL 2012 35