200 BACTERIA, YEASTS, AND MOLDS 



The Open-Kettle Method. The old household method of 

 canning is to stew the material to be preserved, generally 

 with the addition of considerable sugar, and then after a 

 short boiling to pour it while still hot into jars that have 

 previously been sterilized by boiling. The jars are sealed 

 and the process is complete. This method is applicable 

 principally to fruits that contain so much acid and sugar 

 that the bacteria whose spores resist the boiling are unable 

 to grow. Tomatoes are generally put up successfully by this 

 method, although not so easily as fruits. 



The Cold-Pack Method. By the newer methods of canning, 

 as recently advocated by the Department of Agriculture, the 

 food is placed in the jars before heating and is sterilized 

 in the jars. Sterilization is accomplished by heating under 

 steam pressure, by protracted boiling, or by the intermittent 

 method (see p. 194). The finished product is generally im- 

 proved if the food is blanched before packing in the jars, 

 that, is, immersed in boiling water for a short time and then 

 dipped once or twice into cold water. This method is appli- 

 cable to fruits and to nearly all vegetables, but for fruits its 

 advantages over the hot-pack method are perhaps not suffi- 

 cient to recommend it to the housewife who is familiar with 

 the older method. For different foods different periods of 

 heating are recommended, as shown for some of the more 

 important fruits and vegetables on the next page. For full 

 particulars the reader is referred to the circulars of the 

 Department of Agriculture. - ■ 



Even the cold-pack method does not absolutely assure pres- 

 ervation. Some loss must be expected, both through spores 

 that escape sterilization and through bacteria that find en- 

 trance on account of careless handling or poorly sealed jars. 



