HEAT IN THE PRESERVATION OF FOOD PRODUCTS 459 



From Standpoint of Commerce. — In its commercial aspect, the 

 importance of the industry can scarcely be estimated. Canned 

 pFoducts make possible the carrying of larger stores of provisions by 

 armies and navies and expeditions for exploration than would otherwise 

 be pcfesible. 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 

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

 become of much importance until the last decades of the nineteenth 

 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 healthfulness 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 collectively assumed large proportions. 



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

 United States may be gained from statistics for 1914 compiled by the 

 National Canners' Association, and here reproduced by permission. 

 The pack of tomatoes was 15,222,000 cases; of corn, 9,789,000 cases; 

 and of peas 8,847,000 cases. This does not include fruits, the pack of 

 which in California alone in 191 2 was 4,833,900 cases. Nor do these 

 figures include the great variety of other vegetables, fruits from other 

 states than California, preserves, oysters, meats, or fish. The average 

 case holds two dozen cans, and sells at an approximate average price 

 of $2.40. It is apparent from these data that the canning and preserv- 

 ing 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 physital 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 con- 

 sists in submitting the vegetables to the action of hot water for a short 



