Deterioration of Wines.—Nearly all wines are subject to alterations of different kinds, many of them being easily prevented or cured ; some occur naturally, whilst others are accidental. Those are considered to be natural disorders which are not brought about by outside causes, such as ropiness, sourness, bitterness, and loss of colour. Accidental disorders are principally the results of frost, contact with the atmosphere, or taints derived from the cask, mouldiness, and bad eggs. The means employed to correct these disorders have to be modified according t,o the age of the wine, and to the nature and development of the alteration.
When a wine becomes ropy, it loses its fluidity and becomes oily. White wines are most subject to this disorder, and especially those which have not been allowed to complete their fermentation. It occurs chiefly after a rainy season, when the wine contains but little tartar and tannin. It rarely needs special treatment, as the wine usually recovers in the course of time ; if it does not, a good cure is to add 30 grm. of pure tannin dissolved in half a litre of alcohol at 85°, and to whip the mixture well. Sourness is the most common disorder of all wines ; it occurs chiefly in wines fermented in the presence of air. To avoid it, the casks destined to receive wine should always be sulphured, as has been stated already ; great care must also be taken to allow as little contact with air as possible, both during ferrnentation of the must and the several racking operations. It is almost impossible to permanently restore a wine which has advanced far in this malady, since it alrnost invariably reappears after a length of time, however much care be taken to avoid it. The best way out of the difficulty is either to mix it with a sweet wine for immediate consumption or to dispose of it to the vinegar manufacturers.
Bitterness is a common disorder of aged wines and especially of Burgundy ; it is always preoeded by an alteration of colour. It may be remedied by adding to each cask affected, 135 grm. of tartaric acid, or more, according to the degree of bitterness, and from 10 to 15 grm. of tannin. This treatment generally arrests the progress of the malady, and if after eight or ten days it be drawn off into a sulphured cask, clarified, and treated with 200 grm. of well-washed vegetable black, it will probably be restored to its original condition.
One of the principal accidental alterations of wine is the effect of heat. Too high a temperature in the cellar is likely to excite active fermentation in the casks, which frequently results in the bursting of the latter and the entire loss of the wine. To avoid this, a quantity must be drawn
from each cask, and air freely admitted, in order to check the process. Sometimes ice is introduced into the casks, or a quantity of fresh cold water for the same purpose. The most effectual remedy, however, is to submit the wine to two consecutive rackings and clarifications in a well sulphured cask, with the addition, before each racking, of from 400 to 500 grm. of powdered wood charcoal. When, in very cold weather, a portion of the wine has become frozen, it is best to draw off the liquid portion, since that which is solidified is nothing but water and may be removed without injury, the wine being rather strengthened and improved thereby. If the wine be allowed to melt again, the colour will be seriously impaired. The casks into which it is drawn must be well sulphured, and a little tartaric acid may be introduced with advantage, in order to assist in restoring the natural colour.
Taints arising from mouldiness are due to the condition of the casks when filled. Wines tainted from this cause, or from the use of unsound eggs in the clarification, must never be mixed with other wines, or they will infallibly impart their disagreeable taste to the whole mixture. When so tainted, the wine should be racked off, and pieces of well-burnt wood charcoal introduced into the casks to purify it. It may then be racked again on the following day, with the addition of 500 grm. of good oil, well whipped in. It will not be fit to mix away with other wines until it has stood in the cask at least a, week or ten days.
Wines which have been affected with any of the disorders mentioned above, and successfully treated, should be at once disposed of for immediate consumption, since the affection is liable to return, after a lapse of time, with renewed energy. Ropiness is the only disorder which it is possible to effectually and permanently cure.
Bottling.—The secret of bottling wine with success consists in the exercise of much care and cleanliness. The bottles should be sound, clean, and dry, and free from the least trac,e of musti ness. Experience proves that wines bottled in fine, dry weather preserve their clearness and liquidity much better than those bottled in damp weather, or in a, southerly wind. The wine should be clear and brilliant, or it must be carefully fined and clarified before being finally bottled.