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Must
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 fertilizer.
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