If the dull wine has sufficient alcohol, as shown by a pronounced color, add about an ounce of tannin dissolved in alcohol, or the equivalent of tannified wine, and fine it with one to two ounces of gelatine.
Bluish or violet color, accompanied by a flavor of the lees, often occurs in wines of southern countries, and is due to an abundance of coloring matter and a lack of tartaric acid. When the violet-colored wine has a good deal of color, and more than nine per cent. of alcohol, the color may be changed to red by mixing with it from one-sixth to one-fourth of green wine, which contains an excess of tartaric acid, the natural blue color of the grape being changed to red by the action of the acid; then about an ounce of tannin, or the equivalent of tannified wine, should be added, that the color may become fixed, and that clarification may subsequently take place in a proper manner. In default of green wine, crystalized tartaric acid may be used, which is very soluble in wine. A small amount should be first experimented with, in order to learn just how much to use to change the blue of the wine to red, for we must not forget that this acid gives greenness to the wine and thereby renders it less healthful.
If the wines are so weak in alcohol that they have but little color, and that is blue and dull, they have a tendency to putridity. In this case, the blue color is in fact only a commencement of decomposition. It is due to an internal reaction which transforms a part of the tartrate of potash into carbonate of potash. Such wines have a slightly alkaline flavor, and left to themselves in contact with the air, they become rapidly corrupt, without completely acidifying. These wines are of the poorest quality. This disease, which is very rare, may be prevented by using the proper methods of vinification, and by rendering them firmer and full-bodied by the choice of good varieties of vines. In the treatment of such wines, some propose the use of tartaric acid to restore them. This will turn the blue color to red, but will not prevent the threatened decomposition. Mr. Boireau prefers the use of about one-sixth of green wine, which contains an abundance of the acid, and the subsequent mixing with a strong, full-bodied wine.
Putrid Decomposition—Causes.—Wines are decomposed and become putrid, on account of little spirituous strength and lack of tannin. The weakness in alcohol is due to want of sufficient sugar in the grapes—to the excess of water of vegetation. We see, then, that wine is predisposed to putridity when it is wanting in these two conservative principles, alcohol and tannin. Such wine quickly loses its color; it never becomes brilliant and limpid; it remains turbid, and never clears completely, but continues to deposit. The tendency to decomposition is announced by a change of color, which becomes tawny and dull, which gives it, though young, an appearance of worn out, turbid, old wine. Its red color is in great part deposited, and it retains only the yellow. If the defect is not promptly remedied by fortifying, it acquires a nauseous, putrid flavor of stagnant water; and it continues turbid, and is decomposed, without going squarely into acetous fermentation.
How Avoided.—To avoid this tendency, which is rare, means should be employed to increase the natural sugar in the must, and by planting proper varieties of grapes, which will produce good, firm wines, and by choosing proper situations for the vineyard, and employing the best methods of vinification.
Treatment.—Decomposition may be retarded in several ways: First, by fortifying the wines, by adding tannin to them, and by adding a sufficient quantity of rough, firm, alcoholic wine; second, in default of a strong, full-bodied wine, brandy may be added, or better, the tannin prepared with alcohol, so as to give them a strength of at least ten per cent.; third, fining should be avoided as much as possible, especially the use of finings which precipitate the coloring matter, such as gelatine; albumen should be used in preference, as for weak wines; fourth, the movements of long journeys, and drawing off by the use of pumps, should be avoided, for they are apt to increase the deposition of the coloring matter.
The treatment mentioned will retard the decomposition, but will not arrest it, and such wines can never endure a long voyage unless heavily brandied.
Several Different Natural Vices and Defects may attack the same wine, when it should be treated for that which is most prominent.
ACQUIRED DEFECTS AND DISEASES.
Flat Wine—Flowers—Causes.—Flowers of wine are nothing but a kind of mould, in the form of a whitish scum or film, composed of microscopic fungi, the mycoderma vini and mycoderma aceti, already mentioned under the head of Fermentation, and which develop on the surface of wine left in contact with the air. This mould, or mother, communicates to the wine a disagreeable odor and flavor, and also a slight acidity, which the French call évent odor, or flavor éventé, and which may be called flatness. The development of these organisms is due principally to the direct exposure of the wine to the air, which favors their growth by the evaporation of a portion of the alcohol which exists at the surface of the liquid which is exposed, and a commencement of oxidation of that which remains. The result is that the surface of the wine becomes very weak in alcohol, and having lost its conservative principle, it moulds. This mould consists, as before remarked, of a vast number of small fungi. They have a bad flavor, and are impregnated with an acidity which comes from the action of the oxygen of the air upon the alcohol, converting it into acetic acid.