Stéphanie Rollero,* Anne Flesch, Laura Chasseriaud, Etienne Dorignac, Marina Bely, and Arnaud Delaherche
*Fermentis, 137 Rue Gabriel Péri, 59700 Marcq-en-Baroeul, France 
(s.rollero@fermentis.lesaffre.com)

During alcoholic fermentation, nitrogen is an essential nutrient for yeast as it plays a key role in sugar transport and biosynthesis of wine aromatic compounds (thiols, esters, and higher alcohols). The main issue of a lack in yeast assimilable nitrogen (YAN) in winemaking is sluggish or stuck fermentations that promote growth of alterative species and lead to economic losses. However, correcting the N deficiency is sometimes not enough to restore proper fermentation performance. This suggests the existence of other nutritional shortages.

The aim of this work was to study the effect of the timing and the nature of nutrient addition (mineral N [100% yeast derivative] or mixed complete [mineral N and yeast derivative]) on alcoholic fermentation. First, 16 commercial strains were inoculated into Sauvignon blanc grape must deficient in YAN (110 mgN/L) and with reducing sugars concentration adjusted to 240 g/L (potential alcohol content of 14.3% vol.). Fermentation kinetics of strains were then classified into three groups: stuck, sluggish, or complete alcoholic fermentations. New experiments were carried out in the same grape must supplemented in YAN with ammonium (mineral) or yeast derivative products (100% organic or mixed) to get 200 mgN/L. Nutrient additions were made at the beginning of alcoholic fermentation (single addition) or in two additions (50% at the beginning + 50% at the middle of alcoholic fermentation).

Our results show that supplementation with mixed nutrients was more beneficial for fermentation performance than mineral N alone. Fractionated addition was also more effective than single addition. This study highlights the need to think about yeast nutrition from a holistic perspective (N and lipid addition, timing of addition).

Funding Support: Fermentis, division of S.I. Lesaffre