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W i n e s & V i n e s D e C e M b e r 2 0 1 4 77 WineEast Waterloo_Nov10.qxp 8/26/10 11:36 AM Page 1 nutrients can be modified, if necessary, to provide the best chance for a clean fer- mentation. These tests will avoid adding excessive amounts of either component to the fermentation. Unfortunately there is no common predictor for the YAN con- centration, and consequently it should be measured in the fruit or must prior to pri- mary fermentation to ensure that adequate nitrogen is available through the duration of fermentation. There are several analytical kits that can perform these tests, some of which do not require expensive laboratory equipment. The simplest test, known as the formol titration technique, was modified by Dr. Barry Gump, professor emeritus of chem- istry at California State University, Fresno, and currently professor of beverage man- agement at Florida International University, to incorporate this procedure with the titrat- able acidity test that is often run at this time of year. (A description of this test is available at vitisresearch.com/gumptayan. html.) While YAN can be measured in the winery, wine analysis labs can also measure YAN for wineries throughout harvest. Once the amount of YAN is determined, winemakers can select from three different sources for nitrogen-based products to add during fermentation: • Hydration nutrients such as GoFerm or Nutriferm Arom • Complex nutrients including Fermaid k, Nutriferm Advance and Superfood • Diammonium phosphate or DAP Each winery should ensure that they are using commercially acceptable sup- pliers for nutrient additions. While there are several generic nutrient supplements on the market, commercial products are tested regularly for ingredient purity and efficacy. Additionally, technical support is easily available for most of these products. For example, wineries that have questions about GoFerm or Fermaid k could call Scott Labs or their Lallemand sales rep directly. Or wineries that use the Nutriferm product line could contact Enartis Vinquiry directly. Compared to secondary distribu- tors, these employees will have the most knowledge and greatest understanding of their products. Nutrient management strategies are not a 100% guarantee that all fermentations will be H 2 S free. Any fermentation can end up with hydrogen sulfide by the end. Careful observation of the fermentation, with modi- fication of the nutrient additions if neces- sary, can help inhibit H 2 S development and ensure more successful, completed fermentations. With high-YAN situations, including those with musts that have YAN in the range of 300mg to 500mg per liter, winemakers should carefully follow supplier protocols for use of their products. In most cases, this will include using a hydration nutrient at yeast inoculation. Most suppliers will recommend a small, complex nutrient addition about 24-48 hours after inoculation, and perhaps one- third of the way through fermentation. This addition is intended to minimize yeast stress. Many commercial-grade complex nutrients contain a proprietary mix of com- ponents that aid in absorption of yeast in-