Greenness, as the term imports, is caused by want of maturity of the grapes. We all know that acids abound in unripe fruit, and it is only at the time of maturity, and under the influence of the heat of the sun, that they disappear and are changed into glucose or grape sugar.
A green wine, then, is an imperfect wine, which, besides this defect, generally lacks alcohol, body, mellowness, firmness, bouquet, and color, because the incompletely matured grapes contain much tartaric and malic acid, and but little grape sugar and other mucilaginous matter, and because the matters destined to give color to the skins, as well as the aromatic principles, are not completely elaborated.
The only way to Prevent this Defect is to resort to means necessary to increase the maturity of the grape, or to add sugar to the must, neither of which will scarcely ever be found necessary in California, where the defect is not likely to exist, if the grapes are not picked too green.
Treatment.—Where the sourness is not insupportable, the wine may be ameliorated by adding a quart or two of old brandy for each 100 gallons.
The wine as it comes from the vat contains much more free tartaric acid than it contains after the insensible fermentation in the cask, because it combines with the tartrate of potash in the wine and forms the bitartrate of potash, or cream of tartar, which is deposited with the lees, or attaches itself to the sides of the cask. It follows that the wine will be less green after insensible fermentation, at the first racking, than when it was new; but if the greenness is excessive after the insensible fermentation, the wine still contains much free acid. The excess of acid may be neutralized in wines which are very green by adding the proper amount of tartrate of potash, which combines with a part of the tartaric acid to form the bitartrate, which after a few days falls to the bottom, or adheres to the cask. The dose varies from 10 to 24 ounces per 100 gallons of wine. Five or six gallons of wine are drawn out of the cask, and the tartrate of potash is thrown in by the handful, stirring the while as in the case of fining. This treatment does not always succeed; hence, the necessity of preventing the defect when possible.
When the greenness is not very marked, the wine may also be mixed with an older wine, which contains but little acid and plenty of spirit.
Lime and other alkaline substances will surely neutralize the acid, but they injure the wine and render it unhealthy, and should never be used.
Machard lays great stress upon the addition of brandy to such wines, because, he says, the alcohol will precipitate the excess of acids, and will also combine with them to form ethers which give a delicate, balsamic odor to the wine, which is most agreeable. (See [Ethers], [Bouquet].)
Roughness is due to the astringency given to the wine by the tannin when in excess. Tannin is useful for the preservation and the clarification of wines, and those which contain much, with an equal amount of alcohol, keep much longer than those which contain less, and undergo transportation better, and are considered more healthful.
Roughness is Not a Fault, it is rather an excess of good quality, if the rough wines have no after-taste of the stems, bitterness, earthy flavor, acrity, and possess a high degree of spirit, a fruity flavor, and a good color. Such wines are precious for fortifying, and to assist in aging those which are too feeble to keep a long time without degenerating. When kept without cutting, they last a long time, and end well. But they are long in developing.