PRESERVATION OF FOOD. 



(2.) Fractional or Intermittent Sterilization Method. 



(3.) Open-kettle or Hot-pack Method. 



(4.) Cold-water Method. 



Of these methods the one recommended for home use is the 

 Single-period or Cold-pack Method. It is much the best because of 

 its simplicity and effectiveness, and in this book detailed instructions 

 are given for its use. The outlines of the various methods are as 

 follows : 



( i.) Single-period or Cold-pack Method. The prepared vegetables 

 or fruits are blanched in boiling water or live steam, then quickly cold- 

 dipped and packed at once into hot jars and sterilized in boiling water 

 or by steam-pressure. The jars are then sealed, tested for leaks, and 

 stored. Full details of this method are given in the following pages. 



(2.) Fractional or Intermittent Sterilization Method. Vegetables 

 are more difficult to can than fruits because of the presence of spore- 

 bearing bacteria, which are more resistant to heat than yeasts or moulds. 

 These bacteria will live and decompose vegetables even with the exclu- 

 sion of air. They reproduce by spores which retain vitality for a long 

 time even at boiling temperature, and on cooling will germinate. For 

 this reason, therefore, in order to completely sterilize some vegetables 

 it is necessary to boil for one hour on three successive days. The boil- 

 ing on the first day kills all the living bacteria, but does not kill the 

 spores. As the jar cools the spores germinate and the boiling on the 

 second day kills the fresh crop of bacteria. The third boiling is to 

 ensure perfect sterilization. This method is known as the Intermittent 

 Method and is strongly recommended for the canning of peas, beans, 

 corn, asparagus, greens, pumpkin, and squash. Variations in soil, 

 moisture, and climatic conditions from year to year make cause of 

 failure one year when success has always attended the One-period or 

 Cold-pack Method. 



(3.) Open-kettle or Hot-pack Method. Vegetables or fruits are 

 cooked in an open kettle and packed in hot jars. There is always 

 danger of spores and bacteria being introduced on spoons or other 

 utensils while the jars are being filled. This method should never be 

 used in canning vegetables; even with fruits it is not as desirable as 

 cold-pack. 



(4.) Cold-water Method. Rhubarb, cranberries, gooseberries, 

 and sour cherries because of their acidity are often canned by this 

 method. The fruits are washed, put in sterilized jars, cold water is 

 added to overflowing, and the jars are then sealed. This method is 

 not always successful, as the acid content varies with the ripeness and 

 the locality in which the fruits are grown. 



