HEAT IN THE PRESERVATION OF FOOD PRODUCTS. 383 



make possible the carrying of larger stores of provisions by armies and 

 navies and expeditions for exploration than would otherwise be possible. 

 In fact, the stimulus which prompted the investigation of Appert was a 

 prize offered by the French Navy Department for a method of preserving 

 foods for provisioning ships more satisfactory than by pickling, drying, 

 or other methods in use up to that time. 



Although the preserving industry was established in three great com- 

 mercial centers in the United States as early as 1825, it did not become 

 of much importance until the last quarter of a century. There were 

 many hindrances to the progress of the industry, such as the secrecy 

 observed in the process, skepticism of the public regarding the health- 

 fulness of canned foods, the general prejudice against them, and the high 

 cost of production. These obstacles have gradually been surmounted, 

 and at the present time the several branches of the industry have collec- 

 tively assumed large proportions. 



An idea of the importance and magnitude of the industry in the 

 United States and Canada may be gained from statistics for 1909 com- 

 piled by the National Canners' Association, the California Fruit Grower, 

 and Dominion Canners Limited. In the United States the pack of 

 tomatoes was 10,984,000 cases; of corn, 5,787,000 cases, and of peas 

 5,028,000 cases. This does not include fruits, the pack of which in 

 California alone was 3,047,000 cases. Nor do these figures include the 

 great variety of other vegetables, fruits from other states than California, 

 meats or fish. In Canada the pack was estimated at approximately 

 3,000,000 cases. The average case holds two dozen cans, and sells at 

 an approximate average price of two dollars and forty cents. It is ap- 

 parent from these figures that the canning and preserving industry is one 

 of immense value, and that it constitutes a large factor in the feeding of 

 the race. 



ALTERATION OF FOOD. 



PHYSICAL CHANGES. Appearance. Some physical changes attend 

 the conservation of foods by heat, approaching more or less closely the 

 changes incident to the ordinary preparation of fresh foods for the table. 

 In the preserving of some vegetables, notably peas and asparagus, the 

 canner subjects them to a blanching process which consists in submitting 

 the vegetables to the action of hot water for a short time, the object being, 

 first, to remove the mucous substance from the outside and a part of the 



