A manual of home-making

The prcsc^nce of air in a can will not clause (ntnl to spoil, vided the air is sterile, that is, freetl from all living organi A half-filletl can of fruit will keep perfectly if fruit, riin. rubber^^ and cover are sterile, if the air space alx)ve the fruit is stmfe, and if niicro-orgaiiiams cannot ent^jr the can. The precaulioQ soRietinies taken to run a knife or a spcKHi down the? mli^ of i< can in order to remove the few buhliles that may 1h* there, is consequently unnecessary. Unless the s.[K)on or knife has been boiled, its use in removing air may even endanger the kt?cptng qualities of a can of food, for it may hold organisms tlmt thus find their way into the can. It is now known that some micro-organisms that causae foocb to spoil may assume two forms, the spore and the vcgetatiTe fonn. When conditions are unfavorable to their grrowth. they go into the spore form, cease growitig and repnxlucinK, and tie- come inactive and ver>^ resistant to the influence of heat. 1% » their methoii of tiding over a hard time. In' the sjM>re fonn micro-organisms are much more diiBcult to destroy than in the vegetative form, and some of tin dJe to resist for many hours a temperature even us IukIi oil- ing point of water. During a dry season s|)orei* occur much more frequently than usunl on fruits and vegetables, and the difliculties of successful canning may, therefore, be po^^^tly increased. As soon as growth conditions become f '• — when warmth, moisture, and food are suppliixl — ^=]f ;^ii changing over to the active, growing, vegetative fomi, and in their gieater liveliness they lose much of their jjower to resist heat, cold, and other unfavorable influenc<?s. These fact« explain why canned focxls sometimes spoil evt»n after loiip^ boil- ing and careful and complete sealing; the boiling tempemtare may not have been sufficient to destroy the spores, which Hxm change over to the active grow ing state. The problem ol suc- cessful canning is, therefore*, how even the most resistant miotH organisms may lie killed. FOOD PRESERVATION 601 The coniniereial canner has salved the problem of steriliza- tion by the use of steam under pressure. In this way a tempera- ture higher than the boiling point of water, and hence nnore de- struetive, is olvtained. With a sufficiently high temperature, a relatively short time of cooking is required to steriUze food. Equipfnerit for canning. If canning is to be done successfully, even on a small scale, it is necessary to have some equipment that will lighten labor and save time. Such equipment may be bought especially for Fio. 123, — Steriliaer. showing false bottom aa a rack. the purpose, or it may be made from something already on hand. If possible, a canner should be seen in operation before it is bought. If the so-called cold-paek method (page 606) is used, the first and most essential part of the canning equipment i^ a recep- tacle in which the cans of food may l>e steamed or boileij. This receptacle and its parts are generally spoken of as tlie canner or the canning outfit. Caniiers suitable for home use are of four general types: (I) hot-water outfits; (2) steam cookers; (3) water-seal outfits; (4) steam-pressure outfits. While a small hot-water canner may easily be devised at 602 A MANUAL OF HOME-MAKING i i*