244 THE PRESERVATION OF FOOD PRODUCTS. 



way, there is no excuse for their use in any ordinary food products. 

 They are especially to be condemned in milk. 



NON-POISONOUS PRESERVATIVES. 



Salt. Salt is not an antiseptic in any proper sense and it does 

 not destroy bacteria. But it may be a preservative and when much 

 of it is present in a solution, it has a decidedly repressing action upon 

 bacterial growth, and may stop the ordinary putrefactive changes. 

 When used in the preservation of butter and fish, it also has the 

 advantage of imparting a relish to the product. It is 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 is pork preserved in strong 

 salt brine, and corned beef and corned bacon are preserved in much 

 the same way. Ham is partly preserved by salt, and fish wholly 

 so. Butter and cheese both have their keeping qualities increased by 

 salt. But salt used in this way does not kill the bacteria, and any 

 flesh that contains injurious organisms, bacteria or others, is not 

 rendered wholesome by salting. 



Sugar. A moderate amount of sugar checks most bacterial 

 growth, and a large amount even stops yeast growth. Sugar, there- 

 fore, is widely used as a preservative. Since it is in itself a good 

 food there can be no objection to its use as a preservative, although 

 it always changes the taste and nature of the product. Condensed 

 milk may contain 30 to 40 per cent, of sugar. Jellies, preserves, jams, 

 marmalades are all fruits prepared in various ways and mixed with 

 more or less sugar as a preservative. Raisins, figs, and prunes are 

 whole fruits partly dried and preserved by the drying and the 

 large percentage of sugar contained in them. There are practical 

 difficulties in the way of using sugar with some foods, but with 

 others it has its value. 



Vinegar. Acetic acid is another legitimate food preservative, 

 and is extensively used in the manufacture of pickles. The acid 

 gives a sharp taste to the pickles and also largely prevents the growth 

 of the common putrefying organisms. The vinegar is frequently 



