Besides having the proper relative proportions of water and sugar, the must should contain a sufficient quantity of astringent substances, and these, if not present, must be furnished to it. This is necessary to the success of the subsequent operation of clarifying the fermented liquor, which cannot be performed by artificial means without the assistance of these foreign matters. Catechu is the most convenient, on account of its comparative cheapness, and also because it imparts no taste to the drink. The quantity to be added varies, of course, with the natural astringence of the juices, but, as a general rule, a solution of 30 grin. per hectol. (about 20 grains per gallon) is sufficient.
The process of active fermentation should be conducted at a temperature of not less than 15° (60° F.), and not higher than 25° (77° F.), in order to avoid either retarding or hastening the reaction. The process may be carried on in the open air, in vats of sufficient capacity, say 600 to 800 gallons. When the vat is filled to about five-sixths of its capacity, the sugar should be added, if this is necessary, either in the form of good fresh molasses, or of concentrated juice at a density of 28° to 30° Baume'. The solution of eatechu is next added, if the must is found to be wanting in astringence ; a good test is to add a little of a weak solution of gelatine, which, in that case, produces no precipitate, or a very faint one. The temperature of the must, and of the surrounding atmosphem, should then be carefully notel ; the latter should stand at 15° (60° F.) throughout the operation ; that of the must ought to be raised to 18° or 20° (61° or 68° F.), either by the addition of heated must or by steam. Great attention must be paid to these points of temperature.
Although the juices contain minute quantities of a fermenting principle, it is always advisable, though by no means customary, to add a little good brewer's yeast ; 15 to 20 grains per gallon is quite sufficient. It should be mixed first with a little of the must, and then added to the contents of the vat with vigorous agitation. The vat may then be tightly closed, and the process suffered to proceed. In an hour, the contents of the vat arc in a state of brisk fermentation, and carbonic acid gas is disengaged in considerable quantities. It is never necessary either to remove the scum or to agitate the liquor in any way. The process is complete when the disengagement of gas ceases,
and the liquor has fallen in density to 1° or 1°• 5, showing that all the sugar has undergone conversion into alcohol. It is then drawn off into tuns or barrels, where it undergoes another fermenting process. The usual length of the first or active fermentation is about sixty honrs.
The tuns into which the fermented liquor is drawn off hold usually 130 to 150 gallons ; they aro completely filled, and the bung-hole at the top is simply covered with a piece of linen stretched across it. As soon as the fermentation recommences, the particles of suspended matter are carried to the surface and driven out at the bung-hole; by this means the liquor becomes considerably purified. When this process is complete, which may not be for two or three months, the liquor is ready for clarification, which means the entire removal of all the causes of after-fermentation. The cider is &it racked off into clean casks, which have been well sulphured, as already described. Here the process of clarification is performed. If the addition of catechu to the unfermented liquor have been made, the soluble albuminoid substances will be removed, by its means, on the further addition of a little gelatine or albumen ; more than enough to precipitate the catechu should not on any account be added. It is well to subject the cider to another clarification in a few weeks' time, especially if it is destined for sale. After this treatment, cider will keep as well as wine, and if sufficiently rich in alcohol, it will be much improved by bottling.
The conditions of preservation are identical in the case of cider with those of the preservation of wine. When made from ripe fruit containing much sugar, and when there has been enough astringent matter in the must, and the two processes of fermentation have beeu properly conducted, and those of clarifying and racking. have received due attention and care, there is no reason why cider should not be kept for an indefinite number of years, always provided that it be kept in a cool cellar, in good casks or bottles, and well out of contact with the atmosphere.
In concluding this article it will bc well to recapitulate briefly the most important points in the manufacture, and those to which the cider-maker should give his careful attention.