BACTERIOLOGICAL ASPECTS OF DEHYDRATION 113 



prone to develop in the public mind when new food products 

 are put upon the market. The war, however, has changed the 

 attitude of the public in these matters, and it is probable that 

 there will soon be a considerable expansion of the dehydration 

 industry in this country if the products can fulfill the commercial, 

 nutritional and sanitary requirements. 



Although somewhat aside from the main line which I wish to 

 discuss it may be of interest from the standpoint of general infor- 

 mation to observe how dehydration has been utilized in other 

 countries. Little has been done in England or France. In 

 Switzerland there are a few small concerns engaged in the drying 

 of vegetables. In Germany dehydration of foods has had a 

 great expansion since 1900 and to this process may be ascribed 

 at least a portion of the success that country had in meeting the 

 food situation during the war. In 1898 there were three small 

 plants with an insignificant output, largely potatoes and other 

 root vegetables. In 1906 the number of plants in operation had 

 increased to 39, in 1909 to 199, and in 1914, at the outbreak of 

 the war, to 488; in 1916 there were 841 drying plants and in ad- 

 dition about 2000 breweries were using some portion of their 

 equipment in the drying of food materials. By 1917 the number 

 of drying plants had again more than doubled, and the quantity 

 of potatoes alone dehydrated in Germany was more than three 

 times the total crop of the United States. This fact alone sug- 

 gests one of the reasons why Germany was able to maintain her 

 food supplies during the war. It also by inference supports the 

 claims that have been made that drying does not seriously im- 

 pair the nutritive qualities of foods, a point to which I may later 

 return, although the bearing is not essentially bacteriological. 



Let us now turn to some of the biological questions involved in 

 this process of food preservation, considering first the relation of 

 the water content to the growth of microorganisms. Although 

 it has long been recognized that most microorganisms thrive but 

 poorly in substances of low water content, even if those substances 

 are rich in nutrients, definite data on this point are surprisingly 

 difficult to secure. The general impression of the bacteriologist 

 who is familiar with the general literature is that there is much 



