The Yale expositor., 1908-09-11


while studying diseases of wine, Pas
teur discovered that it was sufficient
TO heat wine for a few seconds at a
temperature of 80 degrees to 60 de-
grees c. in order to prevent souring.
Later he found that beer could be like
wise preserved by heating to so de-
grees TO 90 degrees c. The applica-
ton OF this process to various articles
OF food gave rise to the term pas
teurization." Pasteurization of milk
consists in heating it for a short time
at temperature below the boiling
point, and then rapidly chilling it.
The object in heating is the destruc-
ton OF disease-producing germs, and
II the milk were allowed 10 cool
slowly II would remain for a compare
lively long time at 20 degrees to 81
degrees c., the best temperature for
the development Of such bacteria and
their poisonous products. Various
temperatures and times have been rec
commended for Pasteurization, ranging
from 90 degrees to 50 degrees c.. and
from few seconds TO two hours. The
term ''pasteurized" is accordingly in
definite, and should be replaced in
commerce Icy a plain label indicating
the temperature, the time and the date
OF heating. The two dominant fac
tors that appear to control the tenn
perature and time OF pasteurization
are the thermal death points of patho-
genie bacteria and the thermal death
points Of milk ferments The bacteria
should be killed and the ferments
should remain unaffected Ii may be
here noted that considerable expert
mental difficulties surround the deter
mination of the thermal death points
of both bacteria and ferments, and
that concerning the function of milk
ferments nothing is definitely known.
PasteuriZed milk, then, merely means
heated milk, and is not at all synony-
nous with clean milk, pure milk or
good milk PasteuriZation cannot
atone for filth, and cannot preserve
the best milk for any considerable
length of time. Pasteurization is prac-
tised on a large scale in the cream
cries of Europe and America In Den
mark and Germany it is much in evil
dence, and II is estimated that % per
cent. of the total daily milk supplied
to the city of New York is pasteur-
lied. In Denmark, three different
notifications of the process are in
operation: Cd Heating for times vary
ing from Is minutes TO one hour at
IS degrees c. while the milk flows
through an appropriate pasteurizing
apparatus, after which IL is immedi-
ately cooled; (2) heating for longer
time in steriliZed vessels at So de-
grees to so degrees c., when the YES
sells are scaled and quickly cooled;
90 .heating from one-quarter hour TO
one hour at 65 degrees C.. in a tank.
after which the milk passes through
cooler into the vessel from which IL is
sold. A large number OF machines
have been constructed for the quick
pasteurization of milk. In some the
milk is placed in a copper tank pro-
vided with an insulated steam jacket.
The tank contains rotating arms by
which the milk is thrown against the
heated walls. The milk enters at the
bottom and leaves at the top. BY reg
ulating the quantity of milk admitted.
the rapidity of the revolving arms
and the amount of steam, the milk
may be heated as desired. Whatever
apparatus he used, II should be under
the constant observation of reliable
superintendent, easy TO clean, and so
constructed that the entire quantity
of milk, including the froth can be
equally heated to the desired tempera-
ture. The thermometer attached
should be specially tested. From the
pasteurizer the milk Immediately
passes 10 a cooler. which reduces the
temperature as rapidly and as much
as possible.
Milk presents the strange contrast
OF being the most wholesome of all
foodstuffs, and at times one OF the
most poisonous il is the most diff
cult of all foods to preserve and han
die in pure state. in that it is an
Ideal medium for the cultivation OF all
classes of bacteria. The average milk
supplied to large cities is not a safe
food. This is due 10 the ignorance
and Indifference of those engaged in
the dairy business, TO the unclean and
unhealthy cows used for producing
milk. to its insufficient cooling, to
long transportation. TO unnecessary
and frequent handling, TO lack of
proper cleansing and sterilization of
containing vessels and to It's frequent
association with infectious disease.
bacteria enter milk Immediately 1t is