BACTERIOLOGICAL ASPECTS OF DEHYDRATION 121 



Vegetables of the same kind and lot, thoroughly mixed, were 

 subjected in the different types of containers to the four different 

 sets of conditions which I have described. Initial determinations 

 of moisture and microbic content were made, and the samples 

 properly sealed, were left undisturbed for two, four and six weeks. 

 At the end of this period new sets of determinations were made 

 and the material subjected to careful examination for evidence 

 of discoloration, loss of flavor and enzymic activity. Any devi- 

 ation from normal appearance was recorded. While very small 

 increases in moisture may not readily be detected microscopically, 

 any really appreciable increase is evidenced by the changed ap- 

 pearance and texture of the material. Bacterial changes cannot 

 be easily detected unless the increase is enormous, but compara- 

 tively slight development of mold is at once apparent. 



Our data may be summarized as follows: Materials stored in 

 tin and glass containers under all conditions of temperature and 

 moisture remained practically constant in their moisture content 

 and mold content. The bacterial counts generally diminished, 

 sometimes rapidly, sometimes gradually. In other words, bac- 

 teria with proper storage conditions die off slowly. 



Samples stored at 37°C. and high humidity in paper containers, 

 even though they were heavily treated with paraffin showed little 

 or no increase in moisture at the end of two weeks, and often 

 had not doubled their percentage of water in four weeks, whereas 

 in six weeks, the amount of moisture often increased by 400 per 

 cent or even in some instances by 1000 per cent. It is a strange 

 fact, but apparently a fact, that atmospheric moisture will pen- 

 etrate very rapidly through the paraffin containers if exposed 

 four to six weeks, while some containers could be immersed in 

 water and opened at the end of that time without finding any 

 visible water inside the container. The rate of absorption of 

 atmospheric moisture by dehydrated vegetables when directly 

 exposed to moist air is very moderate at first. The acceleration 

 of absorption may be due to heightened permeability of the cell 

 membranes as a result of slight swelling and increased conduc- 

 tivity of the fibrovascular bundles and other types of cellular 

 structures during the early stages of absorption of water. 



