318 AGRICULTURAL BACTERIOLOGY. 



tion of butter, where it also adds a relish to the product. It 

 is also in general use for the preservation of flesh of various 

 kinds. Flesh which is to be smoked is commonly first salted, 

 the salt adding to the efficacy of this method of preservation. 

 Salt pork and salt corned-beef are also preserved by the large 

 amount of salt present in the brine in which they are kept. 

 Salt is also widely used for preserving fish. In the use of 

 salt it must always be remembered that the bacteria are not 

 killed, and that flesh which contains pathogenic bacteria will 

 not be rendered safe for eating by the salting process. 



Sugar is another substance which is of great usefulness in 

 checking bacterial action. In condensed milk it is the large 

 amount of sugar present which prevents the bacteria in the 

 milk from growing and producing their fermentative changes. 

 In the dried fruits, like, raisins, it is the sugar, as well as the 

 drying, which preserves the food, for there is frequently suf- 

 ficient water left in the mass to make bacterial growth possible 

 if it were not for the repressing action of the sugar. Now 

 sugar is in itself a most excellent food and it may without 

 danger be freely used in the preserving of food products. Prac- 

 tically there are some difficulties in the way which prevent 

 the material from being used in a very large variety of food 

 products. Pure sugar is not liable to any bacterial fermenta- 

 tion if it be kept in a strong solution, or if it be in the form of 

 crystals. When in a weak, watery solution it is sure to 

 undergo some form of fermentation, due either to bacteria or 

 yeasts, unless special care is taken to prevent it. Weak sugar 

 solutions may be preserved by evaporating the water. 



Acetic acid is a third substance which is quite freely used for 

 this purpose. This subject has already been referred to on a 

 previous page and may be passed here with the simple statement 

 that it serves two purposes, since the flavor which is added to 

 the food is a matter of equal importance with the preserving 

 power of the vinegar. 



