1262 The Cornell Reading-Courses 



tation of scientific knowledge to the improvement of food conditions. 

 Winter's dietary is no longer distinguished by scarcity of eggs and lack 

 of vegetables and fruits. Not only has Nature been persuaded to prolong 

 her period of production, but also ways have been perfected of protecting 

 and preserving perishable crops of summer. Industries for preserving 

 foods have become of enormous commercial importance, and preservation 

 of food in the home, particularly in the farm home, is a very important 

 part of the housekeeper's responsibility. 



If foods are to be kept successfully from one season to another, 

 it is necessary to have as nearly as possible exact knowledge 

 of the conditions that interfere with their preservation. This state- 

 ment refers not only to fruits and vegetables that we pickle, preserve with 

 sugar, or put up in cans, but to other foods, such as apples, winter vege- 

 tables, and eggs — foods that we are not trying to keep indefinitely but 

 to give a longer season of usefulness. Many of the important practical 

 factors in food preservation were known even to primitive man : that dried 

 foods keep for a long time ; that salt water and smoke have specific proper- 

 ties which aid in food preservation; that foods last better if they are kept 

 cold. It has been left to civilization and to the advance of science to 

 give reasons and to perfect methods. 



Our grandmothers believed that air or oxygen caused foods to spoil, 

 for they learned by experience that when fruits or vegetables were cooked 

 and put away in sealed cans or jars from which all air was excluded they 

 seemed to keep fairly well. If canned food spoiled after such careful 

 treatment it was believed to be owing to some failure to exclude or remove 

 air. Frequent visits of inspection were made to pantry and storeroom 

 in order to ascertain whether any fruit had begun to work; and great praise 

 was given that housekeeper whose canned goods kept well and did not 

 need occasional sorting. 



We know now that merely removing air will not secure the keeping of 

 foods, nor will merely adding air cause them to spoil; we have learned, 

 too, why drying, salting, pickling, and canning are efficient methods of 

 food preservation. 



WHY FOODS SPOIL 



There are two main reasons why foods spoil: first, because of the 

 presence, in or on foods, of small living organisms which feed on them 

 and change them so that they may cease to be desirable and may even 

 become harmful to us; second, because normally there occur in such foods 

 as fruits and vegetables, eggs, meat, and seeds of all plants, certain sub- 

 stances which, although not alive, are the products of living things and 

 have the power of causing fruit to ripen, seeds to start growing, meat to 

 soften, and final decay in all. Any food that is still alive, or that may some 



