CHAPTER II.
MUST.

Must is the name applied to the juice of the grape before fermentation.

Composition.—A good, average must, contains in 100 parts by weight, the following ingredients, and in the proportions as indicated, by weight, according to Dr. Guyot; but the amount of sugar would be considered too small in California:

Pure water,78
Grape sugar (glucose),20
Free acids (tartaric, tannic, etc.),00.25
Salts, or organic acids (bitartrate), 1.50
Mineral salts, 0.20
Nitrogenous, fermentive matter,  .05
Essential oils,
Mucilaginous and starchy substances,

These constituents vary, however, according to variety of grape, degree of maturity, soil, climate, etc.; and some of them may rise in amount to double the average quantity given, or may even, under some circumstances, descend to the one-fourth of it. Although all these ingredients doubtless have important effects upon the quality of the wine produced by fermentation, the acid giving zest and freshness of taste, and the other minor ingredients, smoothness or harshness, as the case may be, yet the principal one that we have to deal with is the sugar, and it is the only one that the practical wine maker will give much attention to, although in those countries where the grape in some seasons does not ripen, the amount of acid is an important element to be taken into consideration in testing the specific gravity of the must. (See [Composition of Wines], for further details.)

Grape Sugar, or glucose, as it is known in chemical language, as already remarked, is the most important element entering into the composition of must, and upon its quantity depends directly the amount of alcohol contained in the wine. The intelligent wine maker, then, who wishes to know what will be the alcoholic strength of the wine produced by the must which he is about to subject to the action of fermentation, will test the must to ascertain what percentage of sugar it contains. This is very easily done by the use of an instrument prepared for the purpose.

Fig. 1.

Hydrometer.

Must-Scale.—A certain quantity of sugar being heavier than the same volume of water—pure cane sugar weighing about one and six-tenths to one of water—it follows that the more sugar there is added to a given quantity of water the heavier it becomes, and the more it will bear up anything floating on it; or, as it is generally stated, the less of the liquid will be displaced by the floating body. On this principle, the specific gravity of liquids, or their weight as compared with water, is ascertained. The instrument employed is known by the general name of areometer, but it is now more commonly called a hydrometer, and various specific names are given to it according to the uses for which it is intended. When constructed for testing the strength of sugar syrups it is called a syrup-scale, saccharometer, pèse-sirop, etc., and those especially for testing musts are called must-scales, pèse-moût, etc. These latter are constructed on the theory that the liquid contains only cane sugar and water—the difference in specific gravity between cane sugar and grape sugar being disregarded—and that its density depends on the quantity of sugar; and although the density of must is somewhat affected by other solid matters than sugar contained in it, yet these instruments, whether syrup-scales or must-scales proper, will give results sufficiently accurate for the purposes of the wine maker, a small allowance being made for the other solids, as hereafter mentioned. There are three instruments which are the most generally used in this country: Oechsle’s must-scale, Balling’s saccharometer or syrup-scale, and Baumé’s syrup-scale, or pèse-sirop. The degrees of Oechsle’s instrument indicate specific gravity in the manner mentioned under Table I; Balling’s indicates percentages of sugar directly; and Baumé’s degrees are arbitrary. (See Tables [II] and [III].) There are other instruments used in France—the gleuco-œnometer, reading upwards for spirit and down for sugar on the same stem, corresponding in degrees to Baumé’s—and the gleucometer, which indicates at once the percentage of alcohol which the wine will contain after fermentation. Baumé’s and Balling’s instruments are better suited for use in California, where the musts often show a specific gravity higher than is indicated by Oechsle’s scale, which frequently is graduated only up to 80 deg., or 19.75 per cent. of sugar. They are all made on the same general plan, and are usually constructed of glass. The instrument consists of a tube about the size of a pipe-stem, terminating below in a bulb or expansion, weighted at the bottom so that it will stand upright and float when placed in a liquid. The scale is marked on the stem, commencing at the top and numbering downward. The first mark is zero, and shows how far the hydrometer sinks in pure water. ([Fig. 1].) As hydrometers are not always accurate, it is safer before using one to have it tested by a chemist or a gauger, as but few others have the necessary skill or the instruments requisite for that purpose. If, however, an instrument which has been tested is accessible, another one can be easily compared with that by ascertaining if both sink to the same point in the same sugar solutions.