Differences between Red and White Wine.—Instead of putting the pomace into fermenting vats, it is taken immediately to the press, and the juice is fermented by itself, free from stems, skins, and seeds, and is therefore not only free from the coloring matter contained in the skins, but also from the numerous matters that are contained in red wine, extracted from the pomace during fermentation. It is true that white wine may be made from white grapes by the process that is employed in making red wine from colored grapes, but then it ceases to be what is commonly called white wine, and possesses all the characteristics of red wine except its color, which of itself has little effect upon the wine, except to change its appearance; for when white wine has been colored by the addition of a small quantity of very dark wine, it remains white wine still in all its other characteristics, and the difference is readily detected by experts.
Hygienic effects of Red and of White Wine.—Dr. Guyot says that white wines generally are diffusible stimulants of the nervous system; if they are light, they act rapidly upon the human organism, and excite all its functions. But they escape as readily by the skin and excretory organs, and their effect is of short duration. Red wines, on the other hand, are tonic and persistent stimulants of the nerves, muscles, and digestive organs; their action is slower and more prolonged; they do not increase perspiration or the excretions, and their action generally is astringent, persistent, and concentrated.
Process of Making.—As the must comes from the press it is either immediately run into casks, or is first put into a vat to settle. In the latter case it is allowed to stand in the settling vat from twelve to twenty-four hours, and a large portion of the yeasty parts settle to the bottom, a thick scum rises to the surface, and the must becomes partially cleared. The scum is then skimmed from the top, and the liquid is drawn off into casks, leaving the heavy lees. By this means a great part of the fermentive matter is immediately removed, and the wine does not ferment as thoroughly nor as rapidly as it otherwise would, and retains a portion of its sugar and its sweetness longer. In the Champagne districts the musts for sparkling wines are thus treated. If the weather is very warm, it may not be practicable to do this, because fermentation will set in before the must has time to settle. If, however, it is desired to make a dry wine, the must is not put into a settling vat, but is run from the press directly into the casks.
The Barrels in which white wine is fermented and stored are generally of small size, of a capacity of from 30 to 150 gallons, or say 50 or 60 gallons on an average, and it is considered in France that it preserves its good qualities in casks of moderate size better than in large ones. It is to be understood, however, that it is considered advisable in most parts of France that white wine should retain a portion of its sweetness and be mellow rather than dry; but if it is desirable to make a dry wine, larger casks may be used for fermenting and storing. (But see [Summary of Rules], below, and [Casks].)
Filling the Barrels during Fermentation.—A question upon which there is some difference of opinion, is whether the casks should be immediately filled to their full capacity and kept filled up during the first fermentation, so that the scum and foam will be thrown out of the bung, or whether a vacant space shall be left in each barrel, so that all the matter thrown up by the fermentation shall remain. The objections to allowing the wine to boil over are that much good wine is thereby lost, and the outside of the barrels and the floor of the fermenting house or cellar becomes foul. When the active fermentation ceases, whatever has been thrown up in the form of a dirty scum will settle to the bottom with the rest of the lees, and is no more injurious than the latter. If, however, the foam is allowed to run over by keeping the barrels full, a portion of the yeasty parts will be thrown out, fermentation will not go on as tumultuously nor be as complete, and the wine will longer retain a portion of its sweetness. So that the practice in this behalf, as in most others where there is a diversity of practices in making white wine, depends upon whether it is desired to make a very dry wine, or one that retains a portion of its sugar. But in the Champagne districts, although they allow the marc to settle, they do not allow it to run over in fermenting.
Pressing and Filling.—The pomace is pressed in the same manner as the marc of red wine, in two or three different pressings. The usual practice is to fill the barrels with an equal amount of must from each pressing, so that the contents of all shall be uniform in quality. If it is known beforehand how much wine can be made from a given quantity of grapes, the requisite number of barrels will be provided for each lot, and the must of each pressing will be equally distributed in all. (See [General Chapter].)
Different kinds of White Wine.—Boireau divides white wines into three classes: dry, mellow, and sweet, whose characteristics depend essentially upon the density of their musts.
In Dry White Wines fermentation is complete, and all the sugar that is appreciable by the taste or the hydrometer, except the small amount changed into other substances, is transformed into alcohol and carbonic acid. The grapes are gathered as soon as ripe, and are not allowed to shrivel. The density of the must rarely exceeds 13° Baumé.
Mellow White Wines are those which preserve a small quantity of sugar after the tumultuous fermentation has ceased, and which gives them mellowness and unctuosity. To produce these wines, it is necessary to increase the density of the must, which is accomplished in the Gironde by leaving the grapes upon the vines until they shrivel and turn brown (white grapes are used), and they are gathered by several successive pickings. The density of the must is from 12° to 15° Baumé. These wines occupy the place between dry wines and sweet wines.
White Sweet Wines (vins de liqueur) are those which preserve a considerable portion of their sugar, which renders them very sweet. And in order that they may retain their sweetness in aging, the must should mark 15° to 20° Baumé.