The alcoholic fermentation proceeds most rapidly at a temperature of about 25' to 26° C. (77-79° F.), or a few degrees above the ordinary temperature, and is retarded by cold and entirely prevented if the temperature is sufficiently high. With ordinary temperatures, the first twenty-four hours after the juice is expressed sees but little apparent change. During this period, however, the yeast cells are multiplying rapidly and the turbidity of the solution increases. Then a change, beginning slowly but increasing rapidly, takes place; small bubbles of gas rise to the surface, and flecks of foam are formed. Finally the solution seems to be undergoing a mild "working" or ebullition (hence the name fermentation, from .ferrere, to boil), and the fermentation is at its height.
The solution is now changed in taste as well as appearance. The sweetness largely gives place to a mild stinging taste as alcohol is formed. Gradually the "working" ceases, as the sugar is used up or the alcohol becomes sufficiently large in amount to inhibit further action by the yeast. The yeast settles to the bottom of the liquid and the fermen tation, except for a slow change, the after-fermen tation, which persists for several days after the active period of change, conies to a stop. The solution thus acted on cannot be further changed by the same organism, but may be again fermented by the acetic bacteria. [See Vinegar, p. 183.] Generally, not over 10 per cent of alcohol may be produced by yeast, and the ordinary ciders and wines contain less than this amount.
The preparation of wine on a small scale has been practiced in this country since its settlement. It is, however, only about one hundred years ago that the first systematic attempt at grape-culture for wine-making was made in North America (except in California, which was not then a part of the United States). The first really successful attempt was made at Cincinnati, in 1825, by Nicholas Longworth, who planted a vineyard with cuttings of the Catawba grape, a native vine taking its name from the Catawba river in North Carolina. Owing to fungous diseases, the industry had to be abandoned at Cincinnati about 1865, but meantime it had been taken up in other parts of Ohio, and in New York and Missouri.
In California, wine-making has been conducted successfully for more than a hundred years. The introduction of foreign vines, which were not suc cessfully cultivated elsewhere, was here immedi ately successful, and, from the first attempt to grow these vines at the Catholic missions in 1771, the industry has developed, until now California produces more than four times as much wine as all the remainder of the country combined.
The making of wine is a process requiring very great care and watchfulness. From the moment the juice is expressed until the product is ready for the market the wine must be treated with scrupulous care. After the expressing of the juice the first fermentation proceeds in vats or barrels, after which the wine is " racked " into bottles, where the finishing and the after-fermentation take place. Deep-seated chemical changes, result ing in the formation of ethers, or substances giving the pleasant aroma and flavor to wines, are brought about during this period, which may be of long duration. In most instances these changes proceed very slowly, so that wine must be several years old before it reaches the highest quality. Attempts have been made to imitate this aging, with its interaction of alcohol, acids and ethers, by the use of electricity and other agencies, but the naturally ripened product is unapproachable in real delicacy of flavor and aroma.
While the principle underlying the manufacture of wine is very simple and easily comprehended, the actual process is one which requires years of detailed study to master, owing to the effect which minute variations in the quality of the grapes, or in the environmental conditions, may exert.
Classification of wines.
Wines may be divided (1) according to color into red and white ; (2) according to the amount of unchanged sugar left in them at the end of the fermentation process, into " sweet " and "dry"; (3) according to the presence or absence of carbon dioxid held in solution under pressure, into "sparkling" or " effervescing," and " still " wines.
Red wines are made from grapes with dark colored skins. The skins are allowed to remain in the fermenting mass, and the alcohol as it is formed dissolves out the red coloring matter. White vines are usually made from light-colored grapes and the skins are carefully eliminated.
Sweet wines are those still containing a consider able amount of sugar after the fermentation is at an end, while on the other hand, those which are fermented out, or have the sugar exhausted in the final fermentation, are called "dry." It is thus possible to have red or white wines which may be either sweet or dry, still or sparkling, and the number of types or varieties is very large, includ ing champagnes, clarets, Sauternes, Rhine wines, Burgundies, sherries, Madeiras and ports. Many of the kinds are named for the province or locality in which they originated.