THE CANNING OF FOODS. 



A DESCRIPTION OF THE METHODS FOLLOWED IN COMMERCIAL CANNING. 



HISTORICAL NOTE. 



Canning is the art of preserving a food product in a hermetically 

 sealed container, the preservation being accomplished through ster- 

 ilization by means of heat. In its highest sense the object is to retain 

 the food in as nearly a fresh condition as possible as to appearance, 

 palatability, and nutritive quality or in the condition in which it is 

 usually consumed. It affords the means of having wholesome suc- 

 culent vegetables or other products at all times and in places where 

 otherwise the cost or the labor of preparation would be prohibitive. 

 The art was evidently of slow development and the result of various 

 dissociated experiments. The real foundation was laid by Spallan- 

 zani, who in 1765 made experiments which disproved the then popu- 

 lar theory of spontaneous generation. These consisted in placing 

 various nutritive liquids in tubes, sealing them, and then boiling in a 

 water bath for an hour. He showed that the liquids remained 

 unchanged as long as the seal was unbroken and free from external 

 air. He therefore concluded that the " eggs " which cause spoilage 

 are somehow carried in the air. This was canning on a very small 

 scale. The experiments also demonstrated that there was a difference 

 in the effect of moist and of dry heat; that whereas life was de- 

 stroyed by water at a temperature of 45 C., in the dry state 80 C. 

 was necessary. 



The first practical application of this discovery was made by 

 Scheele, a Swedish chemist and apothecary, who preserved vinegar 

 by boiling it in jars or bottles and sealing it at once. This was in 

 1782, and at that time the keeping of good vinegar for extracts and 

 other pharmaceutical processes was of much greater importance than 

 can be realized now. There is no record, however, that Scheele 

 carried his work further than the preservation of the pharmaceutical 

 product 



In 1795 Nicholas Appert, a Frenchman of exceptional training in 

 experimental work and of large practical experience in confection- 

 eries, kitchens, breweries, and distilleries, began work on food preser- 



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