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 
