IMPACT OF MINERAL AND ORGANIC NITROGEN ADDITION ON ALCOHOLIC FERMENTATION WITH S. CEREVISIAE

Abstract

During alcoholic fermentation, nitrogen is one of essential nutrient for yeast as it plays a key role in sugar transport and biosynthesis of and wine aromatic compounds (thiols, esters, higher alcohols). The main issue of a lack in yeast assimilable nitrogen (YAN) in winemaking is sluggish or stuck fermentations promoting the growth of alteration species and leads to economic losses. Currently, grape musts are often characterized by low YAN concentration and an increase of sugars concentration due to global warming, making alcoholic fermentations even more difficult. YAN depletion can be corrected by addition of inorganic (ammonia) or organic (yeast derivatives products) nitrogen during alcoholic fermentation.

The aim of this work was to study the impact of the timing and the nature of nitrogen addition (mineral, organic or mixed) on alcoholic fermentation. First, 16 commercial strains were inoculated in 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 in 3 groups: stuck, sluggish or complete alcoholic fermentations. New experiments were carried on in the same grape must supplemented in YAN with ammonium (mineral) or yeast derivatives products (100% organic or mixed 30% organic- 70% mineral) to get 200 mgN/L. YAN 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 showed that supplementing YAN twice with the mixed yeast derivative allowed complete alcoholic fermentations with reduced durations for all strains that initially showed stuck and sluggish fermentations.