Nitrogen Supplementation of Grape Juice. II. Effect on Amino Acid and Urea Release Following Fermentation

¹ Department of Viticulture and Enology, University of California, Davis, CA 95616-8749.

The effect of nitrogen supplementation on the release of nitrogen-containing compounds post-fermentation was investigated in two commercial yeast strains, UCD 522 (Montrachet) and Prise de Mousse. Added nitrogen influenced both the total amount of nitrogen compounds released in the finished wine and their relative amounts. While the total nitrogen present in the finished wine was not significantly different for the two strains, Prise de Mousse released or failed to consume added arginine, leaving higher concentrations of this amino acid in the wine than found in wine fermented by UCD 522. UCD 522 also produced wines with higher urea levels than Prise de Mousse, and in both strains, supplementation with arginine resulted in higher post-fermentation levels of urea. Supplementation with diammonium phosphate reduced urea production by UCD 522 in juices high in arginine, but had no impact on urea levels in juices with a lower arginine content. Diammonium phosphate did not affect urea release in Prise de Mousse under any of the conditions tested. The effect of limited aeration on release of urea and amino acids post-fermentation was also investigated. Aeration of the fermentations resulted in higher levels of most amino acids post-fermentation compared to unaerated controls. However, urea levels were lower in the aerated samples as compared to the control fermentations for UCD 522. Aeration had no significant impact on urea production in Prise de Mousse.

Key words: yeast, amino acid, nitrogen, urea

Submitted on January 22, 1991

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