4. So far as its food substances are concerned, butter is composed
largely of fat, but it also contains water, protein in the form of
casein, and mineral matter. The quantity of water contained in butter
determines to a large extent the weight of butter, since water is
heavier than fat; but as only 16 per cent, of water is allowed, butter
that contains more water than this is considered to be adulterated. As
very little milk is retained in butter, only a small percentage of
protein is found in this food. However, a considerable quantity of
mineral salts are present, and these make it more valuable than most of
the other fats. Because of the nature of its composition--a very high
percentage of fat and a low percentage of protein--butter is distinctly
a fuel food, that is, a heat-producing food. Of course, there are
cheaper fats, some of which are even better heat-producing foods than
butter, but as their flavor is not especially agreeable to some persons,
they are not used so extensively.

In view of the nature of the composition of this food, an ounce of
butter a day is the average allowance for each person when the diet of a
family contains meat and such other fats as lard, olive oil, etc. At the
most, 1/2 pound of butter should be purchased each week for each member
of the family for table use, and fats cheaper than butter should be used
for cooking purposes.

5. PURCHASING BUTTER.--As in the case of milk, in order that the
housewife may judge the quality of the butter she purchases, she will do
well to look into the cleanliness and sanitary condition of the dairy
that produces it. Too much attention cannot be given to this matter, for
if cream becomes contaminated from careless handling, the same
contamination is liable to occur in the butter made from it. Butter that