Having alluded to both sides of the question, it would seem to be a fair inference from the foregoing that the safest course would be, in a hot climate, to gather the grapes as soon as fairly ripe. This may easily be done, where each grape grower makes his own wine, and has immediate supervision of the picking, and has sufficient men to finish it with promptness. But in the case of large manufacturers who buy their grapes and cannot supervise or order the gathering in the numerous vineyards whose crops they purchase, it may sometimes be necessary, when the grapes come in overripe, and it is not desirable to make sweet wine, to add a small quantity of water to insure prompt and complete fermentation. When the necessity arises, great caution should be used, and the necessity should be avoided when possible.
CHAPTER IV.
STEMMING AND CRUSHING.
Diversity of Opinion on Stemming.—There is no subject connected with wine making upon which there is a greater difference of opinion than that of stemming. And it would seem that the diversity of practice is not always caused by the different conditions and exigencies of location, variety of grapes, etc.; but among the different wine makers in the same locality, some remove the stems, and others do not; from which Dr. Guyot infers that the practice cannot be classed among the essential principles governing vinification, but is a mere matter of detail, and that stemming may be practiced or omitted without materially affecting the wine. But Machard, a writer of the Jura, lays it down imperiously as one of the very essentials of good wine making that the grapes should be fermented with the stems, and calls stemming a pernicious practice.
Effect of Stemming.—All agree, however, that the stems, during fermentation, if not removed, yield tannin to the wine, and thereby give it astringency. It is also said to increase fermentation, by furnishing to the must additional germs of fermentation adhering to the stems, and perhaps acting also in a mechanical way, by presenting many salient points, and exposing a greater surface to the action of the ferment.[1] They also add a certain amount of acid to the wine, if green. It is evident that they increase the labor of pressing, by adding to the mass of marc.
Proper Practice.—If, therefore, by reason of the variety of grapes cultivated, or the soil, or situation, your wine is too soft, lacks life and astringency, ferment with all or a portion of the stems; but if your wine is rough, too astringent, it will be found beneficial to stem the grapes. If your grapes lack the fermentive principle, and fermentation is slow and incomplete, leave the grapes on the stem; and in the same way the fermentation will be assisted, if the grapes are overripe.
When the grapes are fermented with the stems, care must be taken that they do not remain too long in the vat, or the wine may acquire a bitter, disagreeable flavor, called by the French goût de râpe, or stem flavor, which is caused by the bitter principle contained therein, and which is dissolved out by maceration.
To Estimate Tannin.—A certain amount of tannin is necessary to the proper clearing of the wine, which is brought about by the tannin combining with albuminous matters, and they are then precipitated, and the wine may be drawn off, leaving them at the bottom of the cask. It is on the application of this well known principle that Maumené gives a very simple method of ascertaining whether the grapes should be stemmed or not. He says: First make a small quantity of wine without the stems, and add tannin, or, what is better, a decoction made by boiling a quantity of stems, and if sensible precipitation is produced, it is better to ferment with the stems, for tannin is wanting; but if the precipitation is not formed, the grapes should be stemmed.
Fig. 3.
Wooden Stemmer.