62 THE CORNELL READING-COURSES 



bacon, for preserving eggs, hams, fish, and the like. Butter and cheese 

 are salted partly for flavor, but largely for the sake of making them keep 

 better. 



(c) Acids protect food from bacteria and give a new flavor that many 

 find acceptable. In making pickles we soak cucumbers in brine and add 

 vinegar and spices to preserve them. The brine sometimes becomes 

 covered with a scum, owing to bacterial growth, and the pickles grow 

 soft through decay; these facts show that salt by itself is not a perfect 

 preservative. The remedy in the case of the pickles is to scald them, in 

 order to destroy micro-organisms. Other acids are known to preserve 

 foods. This is the case with sauerkraut, which is protected from 

 bacterial growth not only by acetic acid but also by lactic acid, produced 

 by allowing bacteria to grow in the sauerkraut. The resulting acid 

 finally destroys the organisms that have produced it, and aids in pre- 

 venting the entrance of others. 



(d) Spices are antiseptic and are added to foods in order to prevent 

 putrefaction. Mincemeat is a good illustration of this practice. The 

 apples and meat would putrefy very quickly were it not for the spices 

 and boiled cider that are added to prevent putrefaction. We add sage 

 and spices to sausage for the same purpose, while fruit cake is kept for 

 a long time by the same means. Hops not only give a nutty flavor to 

 bread and food in which they are used, but also have a slightly antiseptic 

 action. 



Canning 



Canning keeps fruit and vegetables free from all bacterial growth 

 because it first destroys all life present and then provides for complete 

 exclusion of further organisms. As bacteria are found on utensils, in 

 the air, and in water, and all food materials contain them, we first destroy 

 the bacteria by boiling the food, and then seal the can, which has been 

 thoroughly sterilized, in order to prevent the entrance of bacteria. 

 The housekeeper has learned that a single bacterium in a can is sufficient 

 to destroy the entire contents. Formerly she might have said, " I do 

 not lose many cans of fruit in a year." With her present knowledge of 

 the necessity for complete sterilization she may say, " I never lose a can 

 of fruit." 



This statement is made possible only by thorough sterilization and her- 

 metic sealing of the receptacles used in canning. Some articles of food 

 have to be cooked for a long time before becoming completely sterilized, 

 because they contain spores that may resist ordinary boiling. Most 

 failures in canning are owing to the use of insufficient heat or to failure to 

 sterilize all the utensils used, thus leaving spores, which, developing later, 

 will spoil the material canned. Spores get in accidentally. It is necessary 



