Fermentation is Arrested, sometimes, in the manufacture of white wines, by drawing them off into well sulphured casks, using two or three squares of the match, if the fermentation is not very tumultuous; but if it is very active, it may be treated as mentioned below for musts. And in most cases the proper practice is, where wine needs sulphuring, to draw it off into the sulphured cask, and in this way the oxygen contained in the wine is more thoroughly exposed to the action of the gas.
Unfermented Must.—By sulphuring the must, fermentation is prevented, and thereby is produced what the French call mute wine; and it is the must of white grapes as it comes from the press that is more generally subjected to the process. It is first allowed to settle as described in the chapter on white wine, but it must be drawn from the vat as soon as signs of fermentation appear, and bubbles of carbonic acid rise to the surface. And to have the must clear, it must be closely watched, for as soon as fermentation sets in, it becomes turbid. The must should be freed from all fragments of stems, skins, seeds, etc., and should therefore be strained as it runs from the press.
It is Prepared in Two Different Ways.—First, the cask must be scalded, rinsed, and drained in the usual way, and then as much sulphur must be burned in it as can be consumed, or until the match goes out for want of oxygen. Then the cask must be rapidly made half full of the must, and closely bunged. It should then be rolled and thoroughly shaken until the gas has been well absorbed by the juice. The must is then drawn off without allowing it to come in contact with the air (See [Racking]), and into another cask which has been sulphured in the same manner, and is treated as before. While the second cask is being agitated, sulphur is again burned in the one just emptied, until it goes out, and then the must is transferred back in the same manner, and is again shaken. It is subjected to this operation four times, and the cask is finally filled with must treated in the same way, and tightly bunged. The more successful will the operation be, the more the liquid is kept from contact with the air, and therefore this method is preferable to the next. The second method is as follows: burn in an empty cask matches representing a couple of ounces of sulphur; pour in about five gallons of must, bung it up and thoroughly shake; take out the bung and put in another lighted match; if it will not burn for want of oxygen, the air must be renewed by blowing in the cask with a bellows. Then burn the match in the cask, and afterwards pour in five gallons more of must, bung and shake as before. Continue the process till the cask lacks about five gallons of being full. Then five gallons must be sulphured in another cask, and the cask filled up with this and tightly bunged. Of course, the sulphur burner must be shortened as the cask fills up.
Must treated in this manner may be kept for a long time if well clarified, and the cask is well sulphured at each racking, or a portion sulphured when it commences to ferment.
If it is only necessary to keep the must a short time, a portion only, say one-third, need be sulphured. In that case there will be less odor of sulphur, and it will soon pass away.
Clarification and Care of Unfermented Must.—It should be kept in good, strong casks, well hooped and well bunged, in closed cellars of a constant temperature. The casks should be filled every few days with sulphured must; and they should be frequently racked to free them from ferments. They should not be exposed to the air when racking, and should be racked into well sulphured casks. Boireau says that the must may be completely clarified before sulphuring, by introducing about one ounce of tannin per 100 gallons of must, and pouring into the casks before completely filling about a quart of water in which has been dissolved about four tablets of gelatine, and which has become cold.
A Sulphur Flavor is sometimes communicated to must treated as above, and is also sometimes acquired by wines which are put into casks which have been sulphured for some time, without first washing them, and also by allowing the debris of the sulphur match to fall into the cask; this flavor is apt to pass away with time if not very pronounced, or in that case may be removed by racking into a clean cask. But if the wine has a very decided sulphur flavor, it must be disinfected by wood charcoal. Several large pieces[3] of coal well cleaned and well dried are introduced into the cask and soaked in the wine, from which they can be withdrawn by strings attached before putting them in the cask. Forty-eight hours are generally sufficient to remove the flavor; but if necessary, the process may be repeated, by changing the charcoal. In operating on white wines, a large amount of charcoal may be used without inconvenience, but in the case of red wine, there seems to be some danger of depriving it of a portion of its color. Mr. Maumené says, however, that the charcoal is liable to deprive the wine of the carbonic acid dissolved in it, it being an absorbent of that gas, and thereby rendering the wine more subject to the action of oxygen.
Other Substances have been recommended to Prevent Fermentation in a Must, but notwithstanding the disagreeable flavor which is communicated by an excessive use of sulphur, no other agent has been found which is as satisfactory, on the whole.
By Burning Alcohol in the Cask, the oxygen may be removed, but the ferments are not destroyed. Care must be taken to avoid an explosion. Therefore, the spirit must not be poured into the cask and lighted, but must be placed in a small vessel and lowered in through the bung, as in the case of sulphuring.
The Concentrated Aqueous Solution of Sulphurous Acid has been recommended, but Maumené says that not only is its preservation very difficult, but its management is more difficult than the sulphur match, and the chances of its being mixed with dangerous substances are considerable; and therefore no one should think of using it.