Impact of nitrogen addition timing on the synthesis of fermentative aromas in alcoholic fermentation

Abstract

Among the different compounds present in the must, nitrogen is an essential nutrient for the management of the fermentation kinetics but it also plays an important role in the synthesis of fermentative aromas. To address the problems related to nitrogen deficiencies, nitrogen additions during alcoholic fermentation have been developed. At present, they are mainly used to “secure” the fermentation process and avoid slow or sluggish fermentations. The consequences of such additions on the main reaction are well known (Beltran et al., 2005; Jiménez-Marti et al., 2007; Seguinot et al., 2018). However, their impact on the synthesis of aromas has been poorly studied. So, the main objective of this study was to compare the impact of nitrogen addition at different timings on both the kinetics and aroma synthesis. We also studied the effect of the initial nitrogen content of the must and the quantity of added nitrogen. To study the impact of these 3 parameters simultaneously, we used a Box-Behnken design and response surface modeling. Our results indicated that all three factors studied had important effects on fermentation kinetics and aroma production. The most remarkable points were the different regulation of the bioconversion of higher alcohols into acetate esters on one side and of fatty acids into ethyl esters on the other side. It was highlighted that the conversion of higher alcohols into acetate esters was maximum when nitrogen was added at the beginning of the stationary phase. Conversely, the highest conversion of acids into ethyl esters was reached when nitrogen was added close to the end of the stationary phase. This work enables to get a deeper understanding of the regulation of the yeast metabolism. It also underlines the possibility to refine the organoleptic profile of a wine by targeting the addition of nitrogen at a specific time during the stationary phase.