PART VIII.-CANNED VEGETABLES. 



INTRODUCTION AND SUMMARY, 



By H. W. WILEY. 

 SCOPE OP THE WORK. 



In undertaking the study of canned and preserved foods it was the 

 original intention to have the whole of the work included in one publi- 

 cation. After the inception of the work, however, its magnitude was 

 found to be so great as to render the completion of the original plan 

 impracticable. It has therefore been thought best, without waiting to 

 finish the whole of the work on canned goods, to prepare for publica- 

 tion that part of it relating especially to canned vegetables. 



The work with canned vegetables has been directed especially to the 

 methods of preserving, the preservatives employed, the character of 

 the vessels in which the goods are preserved, and to their food value 

 and digestibility. 



METHODS OF PRESERVING. 



A brief history is given of the process of preserving foods by sealing 

 them at a high temperature from contact with the external air. It is 

 shown that it was originally believed that the success of this process 

 was due to the exclusion of the oxygen. The error of this, however, 

 is set forth and the true theory developed, which rests upon the fact 

 that the germs or microorganisms capable of inducing decay of the 

 food are killed by the high temperature. The exclusion of the external 

 air prevents the access of new germs, and thus the foods are preserved 

 simply because the organisms which produce putrefaction can not be 

 introduced. 



It is shown that a temperature high enough and sufficiently pro- 

 longed to kill these germs in vegetables tends to disintegrate many of 

 them and render them less attractive to the eye than when in the natu- 

 ral state. For this reason canners have sought other methods of pre- 

 serving the foods in such a way as not only to preserve them from decay, 

 but also to preserve their natural attractiveness. The preservatives 



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