Must Before it turns to wine The must is merely sugary water (which has a laxative effect). It is obtained from the grape after pressing and is a semi-dense sugary liquid composed of various substances which were in the grape and will be transferred to the wine. It is a living entity containing 80% water and 15-30% sugars, mostly fructose and glucose. The yeasts transform these substances into alcohol during fermentation. To measure the alcoholic strength of the wine before fermentation a hydrometer is used. This instrument measures the quantity of sugars, giving a good idea of how much alcohol will develop. Other substances are also present, such as acids, at 7 to 4 parts per thousand, mineral salts (the potassium acid salt, potassium tartrate, or cream of tartar) and magnesium salts, calcium, sodium and iron, all at 1-3 parts per thousand, nitrogenous substances such as proteins and amino-acids and other substances at a concentration of 1-3 parts per thousand (including vitamins A, C and B group vitamins). The fructose and glucose are transformed into alcohol through fermentation ( at a rate of 59-60 cubic cm of alcohol per 100 g of grape sugar and to carbon dioxide. The first pressing gives the 'flower' must (from 100kg of grapes the aim is obtain 65-70 kg of this type of must); another 5-10% of liquid must is derived from later pressings. The remainder comprises solid residue, which is sometimes sold to distilleries which extract the alcohol or may be used as a fertiliser.