PRESERVATION OF FOOD PRODUCTS FROM BACTERIA. 313 



berries, blackberries, blueberries, and strawberries represent 

 some of the farm products which yield readily to this method 

 of treatment. In fruit prepared in this way the water is not 

 all removed by any means, sometimes as much as 30 per cent, 

 being left. In most cases there is considerable sugar in the 

 dried product which aids in the preservation. In pears there 

 is some 30 per cent, of sugar, while in raisins there is about 60 

 per cent. It must always be remembered that drying does not 

 destroy the bacteria, but only checks their growth, and, if the 

 fruit has been exposed to a possible contamination of patho- 

 genic bacteria, the drying does not remove the danger. This 

 method of preserving fruits naturally affects their flavor and is 

 frequently quite unsatisfactory for this reason, although it does 

 not materially affect their nutritive value. In recent years hy- 

 draulic pressure has been used to extract the water, with results, 

 on the whole, superior to the extraction by simple drying. 



Hay. One of the most important applications of the drying 

 process is the preparation of hay. The fresh grass contains 

 so much moisture that it could not be preserved in masses 

 without undergoing extensive bacterial decomposition, and to 

 obviate this the farmer resorts to the simple method of drying 

 out some of the water. But this phenomenon of drying hay 

 is not always the simple thing which it seems to be, and, in 

 some methods of preparing hay, a fermentation is certainly in- 

 volved. Where the climate is moderately dry and the sun 

 hot, the simple method of exposing the grass to the sun for a 

 few hours is most widely adopted. But such a method is not 

 possible in regions where there is likely to be a large amount 

 of rain, and it is doubtful whether such a method ever pro- 

 duces the best results. Two other methods of preparing hay 

 are in use in different agricultural communities, each of which 

 is dependent upon a fermentative process. 



Burnt Hay. In this method of hay-curing the heat of fer- 

 mentation is depended upon to produce the drying. The 



