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Yeast Strain and Nitrogen Supplementation: Dynamics of Volatile Ester Production in Chardonnay Juice Fermentations

¹ Department of Viticulture and Enology, University of California, One Shields Avenue, Davis, CA 95616.

^* Corresponding author (email: seebeler{at}ucdavis.edu; tel: 530 752-0696; fax: 530 752-0382)

Volatile esters are a major by-product in the yeast fermentation of grape juice and can significantly impact wine flavor. Seven strains of Saccharomyces cerevisiae were monitored for their production of seven important volatile esters during fermentation of Chardonnay juice. Significant differences were observed in the rate of ester accumulation and the maximum and final ester concentrations among the wines made with the different yeast strains. Three of these strains, a "low," "medium," and high" ester producer, were further studied to determine the effects of different types of nitrogen additions on ester production. Chardonnay juice was supplemented with either diammonium phosphate (DAP), a common nutrient additive in the wine industry, or amino acids, and the ester production was monitored in the same manner as for the yeast strain experiment. The kinetics of ester formation for each nitrogen treatment were dependent upon yeast strain (in our experiment only one strain responded to nitrogen addition), and the DAP addition resulted in more significant increases in volatile esters than did the amino acid addition. From measurements of ammonium and amino acid utilization, our results could indicate that in this study, most of the volatile esters were not formed from the degradation of the added amino acids, but rather, at least in large part, by other biosynthetic mechanisms.

Key words: nitrogen, esters, diammonium phosphate/DAP, amino acids, kinetics, yeast