NON-POISONOUS PRESERVATIVES 263 
tion. 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, 
therefore, 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. Rai- 
sins, 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 mixed with spices, both for the purpose of adding 
flavor and of aiding in the preservation. Vinegar pickles will 
not keep indefinitely, for after a time a scum grows over the 
surface. This is made of microdrganisms which gradually 
weaken the strength of the vinegar until the final decay of the 
pickles is only a matter of time, unless precaution is taken to 
prevent the deterioration of the vinegar. | 
Spices.—Many common household spices are more or less effi- 
cient as antiseptics and tend to delay putrefaction. In some kinds 
of pickles spices are used, and mince meat, sausages, and highly 
spiced fruit cakes are preserved chiefly by the spices they contain. 
