Appletons' Popular Science Monthly, September 1899: Vol. LV, May to October, 1899Various
Science
Appletons' Popular Science Monthly, September 1899: Vol. LV, May to October, 1899
Various
Science -- Periodicals; Technology -- Periodicals
So far as can be determined, this method is efficient in destroying
pathogenic bacteria. Its efficiency is of course dependent upon the
length of time that the milk is retained at the high temperature, and
this can be regulated by the rate of the flow of the milk through the
machine. All evidence we have seems to point to the conclusion that a
temperature of 75° C., continued for a few minutes only, so far
destroys or weakens the pathogenic bacteria which are liable to be
found in milk that they need not subsequently be feared as producing
disease. Of course, there are pathogenic bacteria that are not
destroyed by this temperature, but they are not likely to occur in
milk. The germs of typhoid, diphtheria, and tuberculosis are probably
rendered harmless by such treatment, and these are the chief
pathogenic bacteria of milk. Moreover, the other bacteria are very
greatly decreased in numbers, so that the dangers of intestinal
troubles are at least much reduced. In hospitals where Pasteurization
has been adopted the results are as favorable as with sterilization.
The great value of this plan is, however, that it is practical on a
large scale. In Copenhagen it has been in practice for some three
years very extensively. In Denmark the amount of tuberculosis among
cows is very great, somewhat more than half the animals suffering from
this disease. As a result the public milk supply is regarded with more
suspicion than in countries where the disease is less. It is
everywhere recommended that the milk be always boiled before using,
but the bother of treating the milk thus daily makes people unwilling
to do it, and it is doubtful whether the practice is as common as the
physicians think necessary. Some three years ago a company was
organized to meet the public demand for safe milk, and it has adopted
plans by which it furnishes Pasteurized milk on a scale as extensive
as that of the ordinary milk-supply companies. The company has devised
and manufactured two large machines which receive the milk, Pasteurize
it, and cool it in a constant stream, and are capable of treating two
thousand quarts an hour. The milk received by the company is tested
chemically and filtered, and then allowed to pass through one of these
large machines. After this it is placed in glass bottles and sealed
with the company's seal. The heating is done by steam, and the cooling
by brine cooled by an ammonia cooling machine. The greatest care is
taken in cleaning and sterilizing the bottles, an enormous chamber
some twenty feet long and six feet in diameter being used for a
sterilizer. Into this the washed bottles are placed, the chamber
hermetically closed, and then superheated steam is turned in upon
them. Everything connected with the establishment is conducted with
the greatest attention to cleanliness, and upon a very large scale.
The bottled milk is subsequently distributed in ordinary milk carts. A
bacteriologist is constantly testing the efficiency of the machines by
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