Nitrogen-backboned modeling of wine-making in standard and nitrogen-added fermentations

Abstract

Nitrogen has a strong impact on the key bio-mechanisms involved during the grape-must fermentation but also on the synthesis of flavour markers determining the aromatic profile of the wine. This paper first presents a consistent dynamical mass balance model describing the main physiological phenomena implied in standard batch fermentations, i.e. consumption of sugar and nitrogen and synthesis of ethanol. It also includes nitrogen compounds such as hexose transporters. Moreover, a common practice in wine-making is the addition of nitrogen during the fermentation in order to boost and shorten the process duration. A tractable representation of this boost effect has therefore been developed as an extension of the first model. It is apparent that yeast makes a different use of nitrogen depending on the fermentation stage at which the addition is effected, balancing the regrowth of biomass and the synthesis of supplementary hexose transporters. These models have been validated in line with experimental evidence deduced from extensive experimental studies.

Macroscopic modelling of bioethanol production from potato peel wastes in batch cultures supplemented with inorganic nitrogen

“…Figure 8 clearly highlights the existence of an optimal initial nitrogen concentration (''saturation'' point of Taillandier [26]) as above 170 mg/L, excess nitrogen will no longer boost the bioethanol production. The identified value is in the range of concentration typically used in wine-making context [19][20][21][22][23][24] and is very close to the one applied in Experiments 2 and 5.…”

“…Moreover, this model is based on strong assumptions concerning the link between the time evolution of substrate consumption and carbon dioxide and ethanol production. Therefore, this model seems to be too complex for being [22] have developed a model using a classical Michaëlis-Menten formulation to describe the boost effect of nitrogen supplementation during alcoholic fermentation and allowing the determination of the ''saturation point'' introduced in Taillandier et al [26]. However, the biomass production is only explained based on the nitrogen consumption.…”

“…The parameter values of h 1 , h 2 and h 3 are obtained by linear regression based on (22) using only the experimental data. The results obtained for the direct validation and three sets of cross validation are presented in Table 2.…”

“…Hence, the overestimation of the nitrogen addition leads to a significant economical loss, which is due to the decrease of the process yield and also to the cost associated with the nitrogen supplementation. Despite these key roles of nitrogen in fermentation processes, there exist few predictive models including the effect of nitrogen source on yeast metabolism and, most of the time, they are too complex or based on too strong assumptions to be transposed to other experimental conditions [20][21][22][23][24][25].…”

Production, reactivation and nutrient requirements of active dried yeast in winemaking: theory and practice

“…Addition of nitrogen later than this and up to 75% fermentation duration (∼15% initial sugar) no longer stimulates new biomass formation but continues to stimulate CO 2 production and therefore shortens fermentation duration compared with that of ferments that receive no nitrogen addition (David et al. ).…”