n all pasteurized milk as it flows from the machine, there will
remain some living bacteria. The spores will not be destroyed by any
pasteurizing process, and under commercial conditions, vegetating
bacteria are also present. If the milk is not quickly chilled after
heating, these forms will grow, and their development is
particularly hastened by the destruction of the lactic bacteria, the
acid of which would otherwise hold them in check. The result is
that, unless immediately chilled, pasteurized milk spoils almost as
rapidly as though it had not been heated at all. Efficient and rapid
cooling are, therefore, as essential a portion of the process as the
heating itself.

Care should also be taken to protect the milk from contamination
after treatment. Every utensil with which it comes in contact should
be sterilized. The bottles should be thoroughly washed and
sterilized and subsequently protected from dust until used.

=Sterilization of milk.= It is possible to render milk sterile by the
use of temperatures above the boiling point of water, where it is
heated in a closed vessel, in which steam under pressure is
generated. Such milk is often found in the European markets. In our
own country, the only milk of this kind is the so-called "evaporated
milk." In this process sweet fresh milk is evaporated in vacuum pans
to about one-third of the original volume. This is then placed in
tin cans, which are treated, as in the canning of such vegetables as
peas and corn, by heating the milk to 230 deg. or 240 deg. F. for a few
minutes. In this process, the bacteria (spores as well as vegetating
forms) are completely killed, and the milk acquires a brownish tint,
due to the caramelization of the sugar. The appearance of the
product is very similar to cream, and previous to the passage of
the pure food law, it was sold as evaporated cream.

Condensed milk is not wholly free from bacteria, but is sufficiently
thick, by reason of its treatment so that the contained bacteria
cannot grow. They remain dormant in the milk, but as soon as it is
diluted to a normal consistency, growth takes place, and the milk
rapidly spoils. Condensed milk is prepared by adding cane sugar to
fresh sweet milk, then evaporating the mixture to one-third the
original volume, forming a semi-solid product. Syrups owe their
keeping qualities to the same factor, as condensed milk, _i.e._, the
high consistency.

Milk is also preserved by wholly evaporating th