Issue link: http://read.dmtmag.com/i/138003
SOIL REMI COHEN & CELLAR ent. Saccharomyces cerevisiae can be found on grape skins in low numbers, and tends to be found in higher concentrations on winery equipment. There are techniques for encouraging non-Saccharomyces yeast in fermentation. Studies have shown that K. apiculata survived longer in a fermentation at lower temperatures, and that the contributions of non-Saccharomyces yeast to the flavor and qualities of wine should increase with lower fermentation temperatures. This may be related to yeast alcohol tolerance being higher at lower fermentation temperatures. Another factor that increases the longevity of non-Saccharomyces yeast is higher availability of oxygen. Researchers have found that Torulaspora delbrueckii and Kluyveromyces thermotolerans died in fermentations where Saccharomyces was present, due to lack of oxygen. In general, it is understood that many factors affect the ethanol tolerance of nonSaccharomyces yeast, including the availability of oxygen. WHEN TO INOCULATE There may be situations where proponents of native fermentation may want to consider inoculating. When grapes are harvested at very high Brix, a winemaker can select a commercial yeast strain that has tolerance for high-alcohol concentrations and is known to complete high-alcohol fermentations. Native fermentations often have higher volatile acidity, from increased production of acetic acid. This is mostly due to non-Saccharomyces strains of yeast with higher activity of alcohol and aldehyde dehydrogenases, compared to Saccharomyces. This should be taken into consideration when making the decision to go native or not. Rot in the vineyard due to infec- tion by Botrytis cinerea on grapes can lead to the presence of undesirable microbes, including acetic acid bacteria, and a change in the composition and strains of yeast present on grape skins. Although it varies among Botrytis strains and due to other factors, these microorganisms can generate compounds that are suppressive to fermentation by Saccharomyces. In this case, it may make sense to select and inoculate with a commercially available yeast strain that is a strong performer. Rapid domination after inoculation may be essential to ensure that undesirable organisms do not proliferate or deplete essential nutrients. Winemakers who work in custom crush facilities, or in facilities where they have less control over the winemaking and sanitation protocols, or perhaps in facilities making a wide variety of wines and wine styles, may feel more comfortable selecting a commercial yeast strain Products for SO2 and pH/TA Now! Low-cost meters for SO2, pH and TA in wine Vinmetrica's latest additions to its line of products for wine analysis: The SC-100 gives accurate, easy SO2 results – over 500 sold last year! The SC-200 is a rugged pH and TA meter The SC-300 measures SO2, pH and TA! From $165 Assembled in the USA SO2 (SC-100 and SC-300)* pH/TA (SC-200 and SC-300) Accurate to 1 ppm Easy-to-use instrument Accuracy: 0.02 pH and 0.1 g/L T.A. Autocalibrate at pH 3, 4, 7, 10 * Check our product page at www.vinmetrica.com/products Vn ei i tc m ra 1945 Camino Vida Roble, Suite E - Carlsbad, CA 92008 (760) 494-0597 34 V I N E YARD & WINERY MANAGEMENT | July - Aug 2013 w w w. v w m m e d i a . c o m