History of- Canning 433 



work is effectively performed, the contents of the can 

 will remain unchanged for an indefinite period. 



Development of the canning industry. — An applica- 

 tion of the principle involved in canning was suggested 

 as early as 1782 by the Swedish chemist, Scheele, when 

 he advised the exposure of vinegar to the temperature 

 of boiling water, in order to assure its conservation. 

 Some time after this, the Parisian confectioner, Appert, 

 demonstrated that meats, vegetables and other perish- 

 able products enclosed in sealed vessels could be pre- 

 served by placing them for a short time in boiling water. 



The practice of canning was thus established prior to 

 the development of modern bacteriology, for Appert's 

 book, recounting the results of his experience, first ap- 

 peared in 1810. Gradually, the methods of canning were 

 improved; the open tanks, in which the cans were heated 

 to 212° Fahr., gave way to closed vessels, in which steam 

 under pressure made possible the use of temperatures 

 ranging up to 250° Fahr. The higher temperatures are 

 convenient, not merely because they are more effective 

 in destroying the bacteria, but also because they shorten 

 the period of heating. 



The constant improvement of the mechanical ap- 

 pliances and the growing demand for canned goods 

 have both contributed to the wonderful development of 

 the canning industries. Tomatoes, corn, peas, beans, 

 asparagus, okra, succotash, squash, pumpkins, and 

 other products of the garden and orchard are now placed 

 before the consumer in a palatable and succulent state 

 at a time of the year when, a generation ago, they were 

 merely the subject of pleasant reminiscence. 



