Grape musts nitrogen concentrations

However, nitrogen is not the only nutritional factor that influences H2S evolution in grape musts as evidenced by Sea et al. (1998) who reported poor correlations between H2S and must nitrogen concentrations. Metabolic depletion of OAS and OAH could be the result of a lack of pantothenic acid, a vitamin required for the synthesis of coenzyme A (GoA), which is necessary for formation of these precursors (Fig. 1.12). In agreement, pantothenic acid deficiency is known to increase H2S pro-... 

Dizy, M. Polo, M.C. (1996). Changes in concentration of nitrogenous compounds during fermentation of white grape musts at pilot plant scale. Food Sci. Technol. Ini, 2, 87-93. 

The concentration and composition of nitrogen-containing compounds in grape must plays a crucial role in the nutrition of microorganisms involved... 

The experiment in Table 3.6 shows the effect of the addition of alcohol to grape must. It slows the initiation of fermentation and limits the assimilation of nitrogen and the formation of alcohol. Yet the yeasts can continue their activity up to a higher alcohol content, as long as the inhibitory action of ethanol is not excessive. In this experiment, the variation of the glycerol concentration represents significant metabolic modification. As seen in Section 3.4.1, ethanol intensifies the inhibitory effect of an elevated sugar concentration in must. 

When grapes are fully ripe, mineral nitrogen represents less than 10% of total nitrogen, or a few tens of mg/1 expressed in ammonia. Ammonia, or more exactly the NHj ammonium cation, is the form most directly assimilable by yeasts. Its concentration affects the rapidity with which must starts to ferment as well as its potential... 

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