title: Influence of assimilable nitrogen on volatile acidity production by Saccharomyces cerevisiae during high sugar fermentation.
abstract: We analyzed the variability of volatile acidity and glycerol production by Saccharomyces cerevisiae on a large sample of high sugar musts. The production of volatile acidity was inversely correlated with the maximum cell population and the assimilable nitrogen concentration. The higher the nitrogen concentration, the less volatile acidity was produced. An approach to minimize volatile acidity production during high sugar fermentations by adjustment of assimilable nitrogen in musts was investigated in terms of both quantity and addition time. It was found that the optimal nitrogen concentration in the must is 190 mgN.l(-1). The best moment for nitrogen addition was at the beginning of fermentation. Addition at the end of the growth phase had less effect on volatile acidity reduction. We suggest that by stimulating cell growth, nitrogen addition provides NADH in the redox-equilibrating process, which in turn reduces volatile acidity formation.
authors.affiliation: Faculté d'Oenologie, Université Victor Segalen Bordeaux 2, 351 Cours de la Libération, 33405 Talence, France. marina.bely@univ-pau.fr
authors.forename: Marina
authors.initials: M
authors.lastname: Bely
authors.forename: Alessandra
authors.initials: A
authors.lastname: Rinaldi
authors.forename: Denis
authors.initials: D
authors.lastname: Dubourdieu