others must be added preservatives. An unwarrantable prejudice has been
raised in the minds of many persons against the use of preservatives,
but this is due to the fact that the term is not properly understood. In
this use, it means anything that helps to preserve or keep safe the food
to which it is added. Sugar, salt, spices, and vinegar are all
preservatives, and are added to food as much for the purpose of
preserving it as for seasoning it.


CANNING AND DRYING OF FOODS

43. Among the common methods of caring for foods that are to be used at
a future time are canning and drying. CANNING, which is discussed fully
in another Section, consists in preserving sterile foods in sealed cans
or jars. The aim in canning is to prevent the growth of micro-organisms,
and to do this the process known as _sterilizing_--that is, the
destroying of bacteria and other micro-organisms by means of heat--is
resorted to. Canning theories are different now from what they were in
former times. For example, housewives formerly made heavy, rich
preserves of available fruits because it was thought that sugar must be
used in large quantities in order to keep or prevent them from spoiling.
While it is true that the sugar assisted, science has since proved that
sterilizing is what must be done, so that now only the sugar desired for
sweetening need be used.

44. The other method of keeping food, namely, DRYING, depends for its
success on the fact that such micro-organisms as bacteria cannot grow
unless they have a considerable quantity of moisture or water. Molds
grow on cheese, bread, damp cloth or paper, or articles that contain
only a small amount of moisture, but bacteria need from 20 to 30 per