Mineral grape must

Teissedre PL, Cabanis MTand Cabanis JC (1993) [Comparison of two mineralization methods for the determination of lead by electrothermal atomic absorption spectrometry. Applications to soils, vine-leaves, grapes, musts, rapes and lees samples]. Ana-lusis 21 249 - 254 [French]. 

The precise function of only a few minerals is known. Grape must contains, both qualitatively and quantitatively, a sufficient mineral supply to ensure yeast development. 

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... 

Among these components are a number of vitamins and a number of minerals. In addition to the major requirement for nitrogen, phosphorous, and potassium, yeasts also require a wide range of trace elements. These must all be supplied by the grape in order that the fermentation will be rapid and complete. 

The distribution of minerals in the grape berry is not insignificant and it has an impact on the composition of must at maturity. Potassium is essentially located in the pulp cell vacuoles, but the skin cells also sometimes contain significant amounts. 

In conclusion, the primordial influence of soil has been recognized for a long time in the form of viticultural terroirs. The soil must create favorable conditions for grape development and maturation (mineral and water supply and microclimate). The temperature above the soil and its water content also have an impact on the earUness or lateness of the vines growing season (Barbeau etal., 1998 Tesic et al 2001). These two parameters give an initial indication of the quality of a terroir. But a quality terroir must also limit the consequences of weather variations from one year to another. Soil study is difficult since all of the factors likely to influence the biochemical processes of maturation should be taken into account. 

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