Composition of the Must — A very good idea of the qualities of a good. average must may be gained from the following table pre pared by Dr. Guyot: It should be pointed out that these dif ferent ingredients are not always in the same proportion; that some of them may rise to double the average quantity above given, or may fall, in some cases, to one-fourth of it In brief, the composition of the must varies ac cording to the variety of grape, degree of ma turity, kind of soil, climate, etc.
After water, grape sugar or glucose is the most important element of the must. By the agents of fermentation it is transformed prin cipally into alcohol and carbonic acid. This transformation is represented by the following chemical formula: 2CO3 Grage sugar. Alcohol. Carbonic anhydride.
There remains a very small proportion of gly cerine and succinic acid, and matters dissoh ed in the liquid. According to Pasteur, 100 of glucose yield through fermentation: Alco hol, 48.46; carbonic acid, 46.67; glycerine, 33): succinic acid, .61, and other substances left. 1.03 The organic acids and acid salts, while they exist in very small proportions, have great in fluence on the course of fermentation and the quality of the product. The must of grapes picked too soon will contain an excess of ands and a corresponding lack in sugar; while in overripe grapes there will be much sugar hot a deficiency in acids. Therefore, wine-makers endeavor to correct such imperfections by water ing the must, or by adding sugar, or by addinc tannic or tartaric acids, etc. To determine the acidity of must. several instruments, or acid imeters, have been invented Most of them require considerable skill and knowledge to be properly used. hut the Dujardin acidimetric Tube will answer for all practical purposes.
The other substances contained in the mow — all matters, etc.— contribute to the formation of extractive matters, after haring served to feed the yeast organism.
Vinification.—The French word "vindica tion' is a convenient and common term used to cover the details of wine-making. The treatments of the must result in different lei of wines Thus. we have two distinct classes: (1) 'dry' wines, and (2) sweet wines.
Dry wines are those in which the sugar has been fermented out.
Sweet wines are those which, after their ac tive fermentation, still retain a quantity of sugar.
Many of the sweet wines are fortified by the addition of brandy.
Wines are often classed as 'still' and 'sparkling.' Still wines are those in which the carbonic acid gas has wholly escaped. Sparkling wines are those which hold a greater or less amount of carbonic acid gas.
It is useful and convenient to make two classes, namely (a) red wines, and (h) white wines. Red wines are produced from red or other colored grapes, the color being extracted from the skins during fermentation. The color ing matter is purplish blue, but is changed to red by the acids in the must. White wines are produced from both white and colored grapes. In order to avoid dark color, the must is quickly separated from the skins and other solid parts of the grape. The following is briefly the method of vivification of red wines: The ancient method consisted in tramping the grapes with the bare feet or with heavy boots in a big trough from which the juice ran as it was expressed. While this old-fashioned method still obtains in a few dir tries in Europe, it has been superseded there and in the United States by machines, which are called 'crushers.' There are several kind of mechanical crushers, but the type most gener ally used consists of a hopper beneath which revolve two grooved cylinders.
The grapes when dumped into the hopper are then crushed between the tonere, which only break the skins without crushing the seeds. They next pass into the stemmer.
Formerly done by hand, or by a rake over a sieve or screen, the stems are now removed by machines in a very ingenious man ner. The grapes after passing through the crusher fall into the stemmer. The stems are carried to one end of the machine, where they are discharged; the seeds, skins, pulp and juice escape through the bottom, and are conveyed by chutes into the fermenting tanks, which are usually on the floor underneath.
Stemming has its advocates and opponents. The advantages claimed for stemming arc that it facilitates the free access of air and so helps fermentation, especially in case of damaged vintages; that stemmed wines have more finesse and are more alcoholic than wines from un 5ternmed grapes. In the south and southwest of France wine-makers seldom stem their grapes. As a rule grapes arc stemmed in the leading wineries in our Eastern States and in California.