Issue link: http://winesandvines.uberflip.com/i/116287
WineEast What's New in Research Winery Design, Operation, Consulting www.WineDoc.com WINERY PLANNING Business Plans Building Layouts Equipment Specs Winemaking Dr. Tom CoƩrell 800 793-6436 Tom@WineDoc.com OAK ALTERNATIVES - BECOPAD Eastern Distributor for Beco Filter Sheets, Siha Yeast, EvOAK Oak Alternatives, Parker-dh Membranes, Chillers, N2 Generators, Zander Air Products R CENTRIFUGES 94 W in e s & V i ne s APR I L 2 013 - DECAN T E S TERILE FILTRATION - WATER FILTRATIO N - SIHA YEAST - on one vintage on the West Coast of the United States. Commercial yeast nutrient supplements are available to correct nitrogen deficiencies, and analytical tools are available to measure these deficiencies. This study assessed the amino nitrogen contributions of 20 complex yeast foods at manufacturer-recommended doses and found them to range from 8 to 24 mg/L. Analysis of 128 commercial wines showed residual YAN ranged from 11 to 586 mg/L, with hybrid cultivars on average showing higher residual YAN than Vitis vinifera. Nitrogen utilization varies greatly among native and commercial yeast strains, and juices from hybrid cultivars in the Midwest and East can have both relatively low sugar and high nitrogen concentrations at harvest, which may contribute to high residual YAN. Residual nitrogen available following alcoholic fermentation can provide a significant nutrient base for spoilage organisms, particularly surface yeasts and Brettanomyces spp. To further investigate differences in yeast nutrient status between V. vinifera and hybrids, amino acid profiles were determined for several cultivars. Amino acid profiles of several hybrid cultivars were substantially different from the generally reported profile for V. vinifera. Some follow-up work (Stewart and Butzke, ASEV-ES 2012) examined amino acid profiles and YAN in hybrid winegrapes from the eastern U.S. and showed that there were substantially different amino acid profiles in winegrapes common to the eastern United States. Comparison of profiles from hybrid varieties with V. labrusca parentage versus those of V. labrusca varieties suggested that amino acid profile is heritable. This relationship is also being investigated for V. riparia hybrids and V. rotundifolia (Muscadines). Amino acid profile should be considered when designing yeast nutrients for hybrid and native winegrape applications. They also surveyed YAN in winegrapes across several Midwestern and southern states, and found a range of 89 to 938 mg/L across one vintage, more than 30 grape varieties and four states. For some varieties, average YAN far exceeded previous recommendations based on initial sugar content (200-, 250-, or 300 mg/L YAN at 21o, 23o—or 25o Brix, respectively). Understanding the differences in amino acid profile and total YAN concentration between hybrids and V. vinifera is essential to developing targeted fermentation management strategies. Dr. Anna Katharine Mansfield is studying the concentration of yeast-assimilable nigrogen in Finger Lakes Riesling. Predicting harvest concentration of yeast-assimilable nitrogen in Finger Lakes Riesling. The enology program at Cornell (Geneva) also has focused, among many things, on yeast nutrition. Drs. Anna Katharine Mansfield (above) and Ramón Mira de Orduña are the main individuals investigating this issue. This project was presented at the ASEV-ES meeting in Towson, Md., in 2011 and was conducted by Mark Nisbet et al. of Cornell University's New York State Agricultural Experiment Station in Geneva. It involved a survey of 77 commercial Riesling vineyards to determine the range and variation in YAN concentration in New York and to develop a method for predicting the final YAN concentrations prior to harvest. YAN, comprised of ammonia and primary amino nitrogen, is a measure of the nitrogen available for yeast biomass production and is often the limiting nutrient in alcoholic fermentation. A deficiency of YAN in grape musts is common in the New York wine industry, but because YAN analysis is difficult and time consuming, many producers make nutrient additions without determining initial must YAN concentration. Over 80% of the Riesling samples obtained in the survey had YAN concentrations less than 140 mg nitrogen per liter, the minimum concentration recommended for healthy fermentation. Riesling samples collected from 61 commercial vineyards at three time points throughout the growing season (pre-