Ipek Aktuna, Jonathan D. Brumley, G. Candan Gurakan, and Charles G. Edwards*
*Washington State University, School of Food Science, Pullman, WA, 99164-6376 (edwardsc@wsu.edu)

 Metschnikowia pulcherrima and Saccharomyces cerevisiae can be used in either sequential or co-inoculation to produce wines containing lower amounts of ethanol. Like S. cerevisiae, M. pulcherrima requires a range of nutrients such as amino acids and ammonia (collectively referred to as yeast assimilable nitrogen, or YAN). Due to limiting YAN concentrations present in grape musts, there is competition between these yeasts for nutrients. In this work, M. pulcherrima P01A016 was inoculated sequentially with a commercial strain of S. cerevisiae (Lalvin NBCTM) to determine the effects of the timing of nitrogen addition on fermentation. Using a commercially prepared Chardonnay must, a completely random experimental design was applied, with N addition time as a variable (day 1, 3, or 5 after M. pulcherrima inoculation). All Chardonnay wines reached dryness by day 31, exception those without N addition. The addition of N prior to S. cerevisiae inoculation (day 1 or 3) resulted in increased biomass production over treatments with N added on day 5 or without N addition. Overall, M. pulcherrima greatly depleted the Chardonnay must of YAN prior to inoculation of S. cerevisiae in all treatments, even when N was added on day 1 or 3. This result indicated that M. pulcherrima has a high N requirement and care must be exerted when using this yeast with S. cerevisiae, especially in grape musts containing low amounts of N.

Funding Support: Washington State Grape and Wine Research Program, the Northwest Center for Small Fruits Research, and the Ph.D. scholarship of Turkish Higher Education Council (YOK 100/2000).