When cider is left standing for a short time, the length of which depends largely upon the temperature, fermentation sets in and the cider becomes hard, that is, the sugar which it contains is converted largely into alcohol and carbon dioxid. The taste of the cider changes, it loses its sweetness, it acquires a sharp, penetrating taste due to a combination of alcohol and carbon dioxid, and becomes intoxicating. Hard cider is often used as a beverage, and its activity apparently is increased by the raw products of fermentation which it contains. If hard cider could be stored in wood in such a way as to avoid acetic fermentation its taste and flavor and general character would improve, just as beer is improved by being placed in lager or distilled spirits by being kept in wood. The character of the fermentation depends upon the character of the natural yeasts which are distributed everywhere and which are attached to the fruits before they enter the press. These yeasts are usually of a character to produce a good product. They may be, however, of a bad character. Thus all kinds of flavors may occur in self-fermented ciders.

In localities where the cider industry is carried on as a profession, as, for instance, in Normandy, in certain parts of Germany, and in certain localities in England, steps have been taken to control the character of the fermentation so as to produce always a finished product of an agreeable taste and flavor. Professor W. B. Alwood1 has studied the effects of different kinds of yeast upon the character and flavor of the product. These yeasts he secured by visiting the localities in Europe where pure cultures are used in the manufacture of cider. These living yeasts were brought to this country and cultivated in the laboratory at Charlottesville, which is under the immediate direction of Prof. Alwood. In the preparation of apple juice for the introduction of pure cultures it is first pasteurized so that all the yeasts which it contains are killed. It is then seeded with the pure culture and left to fermentation in the usual way.

1 Bureau of Chemistry, Department of Agriculture, Bulletin No. 129.

The content of alcohol developed in hard-cider making depends, of course, upon the amount of fermentable matter present. In low-grade apples, grown in Nebraska, Gore1 found the following average composition of several varieties, including those which are commonly grown: York Imperial, Black Twig, Winesap, Rhode Island Greening, Grimes Golden, Jonathan and Ben Davis. These apples were all unmerchantable and therefore may be regarded as the waste material of the orchard. The average composition of the juices of these varieties is as follows:

These data may be taken to represent very accurately the ordinary materials, culls, specked apples, windfalls, etc., which are used in the United States in the making of cider.

The cider was made under the supervision of Prof. Alwood in the most approved manner, and a very fair article of bottled cider was secured. The cider was made during hot September weather, and after racking and storing in sterilized barrels and kegs analyses were made in the following April. The different lots contained the following percentages of alcohol: Lot 1, kept in kegs, 5 percent; stored in barrels, 4.84 percent. From the above data it is seen that a cider properly fermented and protected from acetic fermentation by proper storage produces almost the theoretical percentage of alcohol which could be expected.

1 Journal of American Chemical Society, 1907, Volume 29, page 1112.

Theoretically a sugar will produce one-half of its weight in alcohol. An 11 percent sugar would be expected to produce 5 1/2 percent of alcohol. In point of fact all of the sugar is not converted into alcohol. During fermentation some of it is converted into organic acids and other products, and a little of it always escapes fermentation.

In order to produce a sparkling cider the final fermentation is allowed to take place in a stoppered bottle in the same way that champagne is made, though of course the pressure is not usually so great. Hard ciders made in this way produce a fine foam, and their potable qualities are greatly benefited by finishing the fermentation in the bottle. Ciders which are fermented in the manner described, so as to be clean and free of germ life except that necessary to produce the final fermentation, keep perfectly in the bottle. Alwood found that the samples thus made were in excellent condition at the end of two years. Ciders made from winter apples and allowed to ferment, either through their own yeasts or by the addition of yeasts, were found to keep perfectly, although in many instances the fermentation was stopped before all the sugar was consumed. The apples from which the winter juices were made contained more sugar than those of the low-grade apples, namely, a little over 12 percent. The percentage of alcohol obtained was generally about 5 percent, though in one instance it fell to 3.64 percent by weight and rose as high as 5.12 percent by weight in another.

These valuable researches of Alwood show beyond any doubt that it would be possible in this country to make a cider, especially a bottled cider, containing approximately 5 percent of alcohol, which would be quite equal to the best sparkling ciders made in Normandy.