DISTILLATION

is, in its fundamental features, the vaporizing of a liquid by heat in one vessel and then conducting the vapor or steam into another cool vessel, where it is condensed into a liquid. The value of the process is found in the fact that very few liquids become vapor at the same temperature. Ethyl alcohol will vaporize at 173 degree Fahr., and water at 212 degree--so that each can be readily separated from the other or from other components.

Distillation in its simplest form, may be explained by remarking that if one places a kettle of wine, for example, on a stove, the steam which comes out of the spout prior to the water-boiling point, 212 degree Fahr., is principally alcoholic vapor, which, if passed into another vessel and held until it condenses into a liquid, will be a crude brandy. A simple distillation will not produce a complete separation--the alcoholic vapor passed out contains a certain percentage of water--but the process can be repeated until nearly all water is eliminated. A complete separation can only be secured by placing the liquid, after distillation to the highest possible percentage, in suspended skin bags. The water, being heavier than the alcohol, settles to the bottom and gradually drips through the bag.

The principal use of the process of distillation is for the manufacture of commercial alcohol and liquors such as brandy, whisky, rum, etc., and to add special flavors and properties to alcoholic liquors, as in the manufacture of perfumes, liqueurs, etc., but it is also employed to separate light and heavy oils, in the manufacture of certain products from coal tar, to purify drinking water, to separate volatile from non-volatile substances either in watery or alcoholic solutions or mixtures, etc. Another familiar example is the changing of sea water into fresh water by distillation--the fresh water passes over as steam, leaving the salt behind.

In the manufacture of brandy, rum, whisky, etc., distillation is preceded by other processes which produce a fermented liquid consisting of alcohol, water and solids, it being the duty of distillation to separate the alcohol and water from the solids and then to eliminate a part of the water and certain other volatile substances. Brandy is made from wine (the fermented juice of grapes); rum from fermented molasses and other residue of sugar manufacture; whisky from a fermented grain mixture (see article on WHISKY).

The fermented liquid is placed in a "still." The old-fashioned pot-still consists of a large round pot with a short copper "chimney" for the vapor, with a bend at the top and a horizontal continuation in the shape of an elongated neck or spout. The still is heated to 173 degree Fahr. and over, by direct fire beneath in a brick "oven" surrounding steam pipes running back and forth through the chamber of the evaporator. The advocates of this process claim that the heat is more evenly distributed and the temperature more uniform, avoiding all danger of scorching the fruit.

In order to secure the best results of evaporation it is necessary to run the temperature as high as possible without injury to the fruit and to keep the air in rapid circulation throughout the chamber. It is under these conditions that the slight chemical changes in perfectly evaporated fruit take place--the albumen, instead of being slowly dried, is coagulated and greatly assists in the preservation of the fruit with the richness and flavor it possessed in its natural state. After the trays are removed from the evaporator, the fruit is put into bins where it is stirred occasionally and allowed to remain until it has passed through the sweating process. Next comes the grading, by appearance, quality, etc.

Apples are generally peeled, cored and sliced by special machines before being passed to the evaporator. Pears and peaches are usually cut in halves and evaporated with or without being peeled.

The cores and skins are evaporated separately, but in the same way as the fruit. When properly cured, they possess commercial value in home and foreign markets for the manufacture of jellies and vinegar.

Standards, etc. Much trouble formerly arose from the lack of a standard of dryness in evaporated fruit. A bushel of green apples, for example, weighs about 50 lbs. and should make 7 or 8 lbs. of white stock and 4 lbs. of waste--five-sixths of the fruit being water. Apples when thoroughly dried still contain about 25% of water, but many lots were formerly sent to market containing 30 to 35%--being only half dried, they molded, discolored and fermented or soured. The present food law fixes 27 1/2% as the limit, which has practically eliminated that particular trouble--to the great advantage of the industry as a whole.

During the Summer months and in warm climates generally, dried fruit is best kept in cold storage. If in good condition when put in, it will maintain its quality, flavor, etc., for a long time. If held in stores where it is exposed to dampness, it is liable to sour or become moldy.

Preparation for the Table. In preparing dried or evaporated fruits such as apples and peaches for the table, the best results are attained by cooking slowly for several hours at a temperature just below the boiling point, enough water being added at first to cover the fruit. Every package of dried fruit should bear printed directions for making pies and for other forms of cooking, as very few housewives know how to use it to the best advantage.

See also articles on APPLES (dried), DATES, FIGS, PRUNES, RAISINS, etc.