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86 WINES&VINES April 2016 WINEMAKING WINE EAST by differences in microbial ecology. Hansenias- pora uvarum and species of Kluyveromyces were isolated in both vineyard samples, but the dis- tinctions in resident winery microflora were more marked. Winery 1 had overall greater yeast counts than Winery 2, and S. cerevisiae was identified in some of the isolates. Although two Candida and one unknown yeast species were identified on equipment in Winery 2, no yeast or bacteria was detected on clarification and fermentation tanks. The presence of S. cerevisiae at Winery 1 may help explain the rapid commencement of fermentations there, as winery microflora would be well adapted to the environment, and S. cerevisiae strains rapidly dominated all fermentations. Total non-Saccharomyces population was lower and quickly declined. The long lag phases (averaging 28 days) in Winery 2 may have been due to lower initial S. cerevisiae populations, as the non-Saccha- romyces population in those wines was found to be more diverse and peaked at the same population as the S. cerevisiae. Among the eight S. cerevisiae isolates, five commercial strains were identified, most of which had been used previously in the winery in which it was found. Different strains were isolated from different fermentation stages, suggesting that no single strain dominated fer- mentation. Some of the non-Saccharomyces spe- cies identified in the vineyard, equipment and fermentation samples were detected through advanced stages of fermentation. H. uvarum was isolated when fermentations had 5° Brix of residual sugar, or approximately 7.7% ethanol; Kluyveromyces was detected at the end of fer- mentation (10.2% ethanol) in one wine. Other non-Saccharomyces yeasts were present in fer- menting musts, including Pichia. fermentans, which survived until approximately 5% ethanol, unknown Hanseniaspora and Torulaspora spp., P. anomala and Dekkera anomala. All wines were of commercial quality and have been released for sale in their respective tasting rooms. Future…spontaneity? The current reexamination of spontaneous fermentation methods and effects have greatly increased understanding of underly- ing processes, but plenty of questions—both scientific and stylistic—remain. The sheer number of yeasts and bacteria that can colo- nize in vineyards and wineries ensures that microflora will vary by region, winery and even grape cultivar, with each mix as variable as the harvest season that spawns it. Re- search examining yeast-yeast, yeast-bacteria and bacteria-bacteria interactions continues, as do investigations of the nutritional needs of mixed-colony fermentations. At the same time, advanced techniques in yeast genotyping are providing new in- sight into the origin of S. cerevisiae, the concept of "microbial terroir" and the role yeast play in "natural" winemaking. One thing is for certain: Spontaneous fermenta- tions are likely to produce a wider palette of sensory characteristics than are usually found in inoculated fermentations, but whether those characteristics are positive or negative is dictated by factors we don't yet fully understand. Anna Katharine Mansfield, PhD., is an associate profes- sor of enology in the food science department at Cornell University's New York State Agricultural Experiment Station in Geneva, N.Y., and Camila Tahim is a recent master's degree graduate of the same department. RESOURCE NOTE A thorough list of yeasts that can contribute to wine sensory character- istics is available from the University of California, Davis. Visit wineserver. ucdavis.edu/industry/enology/winemi- cro/wineyeast/index.html. SUPPORT RESEARCH & WINE INDUSTRY NEEDS THROUGH THE A M E R I C A N V I N E YA R D FO U N D AT I O N P.O. Box 5779, Napa, CA, 94581 • T: (707) 252-6911 Visit our Web site at www.avf.org for information on funding and current research projects A S S E S S M E NTS O F D I F F I C U LT TO F E R M E NT J U I C E S Dr. Linda Bisson examined the causes of chronically difficult to ferment juices. These problem fermentations do not appear to respond to nitrogen or other commercial nutrient addition, occur regardless of yeast strain used, and are challenging to restart the fermentation. For more information visit AVF.org or contact Dr. Bisson at lfbisson@ucdavis.edu. For a wealth of useful viticulture and enology research and information, visit AVF.org, ngr.ucdavis.edu, asev.org, iv.ucdavis.edu or ngwi.org Finding Solutions Through Research