Analysis: Grapes and must

Traditional analysis of grapes and must is chiefly concerned with just three components: sugar, acid, and ph. For table wine, for instance, the grapes should ideally contain sugars capable of producing wines with an alcoholic strength between about 10 and 14% by volume, which means that the grapes should have between 18 and 25% of fermentable sugar by weight (see must weight for the various ways in which this can be measured).

The acidity of the grapes or must should also ideally be such that the total acidity is in the general range of 7 to 10 g/l expressed as tartaric acid. Some acid is always lost during winemaking, primarily as the alcohol content of the wine increases and the solubility of wine acids decreases. Acidity may be further reduced by malolactic conversion and cold stabilization. It is therefore necessary to start with more acid in the grapes than is eventually wanted in the wine. However, it should be noted that the production of succinic acid during fermentation may occasionally lead to a very slight increase in total acidity.