News You Can Use
YAN – Yeast Assimilable Nitrogen
Mark Nesbitt, former graduate student at Cornell University, sets up the ChemWell analyzer to measure YAN in grape juice samples.
Photo: Tim Martinson, Cornell University
In addition to sugars, adequate yeast assimilable nitrogen (YAN) concentration is required for successful alcoholic fermentation of grape musts. Unlike sugars, however, YAN is difficult to measure and impossible to estimate. YAN also varies widely by cultivar, year, climate, harvest date, and viticultural practices. Too little YAN can result in stuck fermentations or production of off-aromas, such as H2S, but too much YAN (which can happen, especially when prophylactic YAN additions are made) can lead to problems with spoilage organisms or production of fusel alcohols.
Recently, much work has been done in the Cornell University Extension Enology Lab to determine YAN concentration of different cultivars in locations across the state, and if YAN levels can be predicted prior to harvest. In the last couple of years, cold-hardy hybrids have been included in this analysis as part of the Northern Grapes Project. Further, research wines are made with the cold-hardy hybrids with varying YAN additions, which are analyzed for TA, pH, % ethanol, organic acids, and residual YAN. Wines will also be subjected to sensory difference tests to determine the impact of YAN concentration.
This issue of News You Can Use contains links to a Research Report from the Year 3 Northern Grapes Project Progress Report covering the YAN work being conducted in Dr. Anna Katharine Mansfield’s lab, as well as a webinar on YAN given by Dr. Mansfield in February 2014.
– YAN Research Report: http://northerngrapesproject.org/wp-content/uploads/2015/02/YAN.pdf
– YAN Webinar: https://www.youtube.com/watch?v=AsdYaxvP3gw
Further, links to other articles about YAN, published in past issues of Veraison to Harvest (published by Cornell University Cooperative Extension viticulture and enology team) provide further background information and other research projects
– http://grapesandwine.cals.cornell.edu/sites/grapesandwine.cals.cornell.edu/files/shared/documents/Veraison-to-Harvest-2009-6.pdf. (See “YAN, the other harvest parameter (that we mostly pretend doesn’t exist,” pg. 2-3, 8)
The Northern Grapes Project is funded by the USDA’s Specialty Crops Research Initiative Program of the National Institute for Food and Agriculture, Project #2011-51181-30850
Chrislyn A. Particka, PhD
Extension Support Specialist
School of Integrative Plant Science, Horticulture Section
630 W. North Street
Geneva, NY 14456