The Yale expositor., 1908-09-11

exposed to the atmosphere At the
time OF milking this exposure is great
est. While perhaps it is impossible tc
avoid wholly the introduction of bac.
terra during milking, If proper pre-
cautions be taken the number intro
duced may be relatively small. Bac-
terra reach the milk from the teat,
udder and body of the COW, from the
hands, body and clothing of the milk
er, with the dust from the atmosphere,
from particles of excrement or litter
which enter the pail and from the
pail itself. The action of these bac-
terra may he considered broadly as of
three types: Cd The large group of
so-called Tactic bacteria produces lac
tic acid from milk sugar, which acid
precipitates the principal protein Of
milk, causing the well-known curdling
or souring. This always occurs when
milk is exposed 10 the air and kept at
temperature above ten degrees c.
These organisms as group are harm
less, as are also the products of their
growth. They, moreover, render good
service by inhibiting or crowding out
the very harmful putrefactive bacteria
which so frequently reach milk from
eXcreta. These nOn-sporing organisms
are killed Icy most methods of pas
teurization, while the sporting putre-
factive organisms are not killed by
any method. II is obvious, therefore,
that a pasteurized milk containing
putrefactive bacteria such as the b.
aerogenes capsulatus or the b. putri-
ficus of Bienstock, is in a much less
protected condition than raw milk. 90
Another group of organisms produce
butyric fermentation, also an acid
change. These grow best at a tenn
perature approaching that of the hui
man body, and produce spores which
resist the temperature of boiling wa
ter for some time. The products of
their growth produce serious disturb
ance in the intestinal tract of man,
more especially of children. The
spores of the germs of butyric fer
mentation are not killed by pasteuri-
cation. CD Several micro-organisms,
including the two mentioned in %,
produce putrefactive lamentations
alkaline changes which proceed in
milk without indications visible to the
naked eye. These spore-bearing or
ganisms are not destroyed by pasteuri-
zation. Too frequently milk comes in
contact with organisms of specific dis.
ease e. e.. tuberculosis, typhoid fever.
diphtheria, etc. PasteuriZation for 20
minutes at 60 degrees to 60 degrees G.
according 10 Rosenau, or 20 degrees
to 80 degrees c. for a shorter period
according 10 Jensen, will effectually
destroy all such organisms.
The length of time during which
milk will keep-that is, the length OF
time which must elapse before suffi-
cient numbers of bacteria develop 10
produce perceptible changes in it's
a function of two factors, temperature
and the initial number of bacteria
present Under ordinarily favorable
conditions, the number of bacteria I'm
milk freshly drawn from a healthy
COW will vary between 500 and 20. 900
per cubic centimeter Mix can be
produced by commercial methods
I
terra per cubic centimeter. On the
other hand, carelessly produced. the
number may reach 500, 100000 Since
most consumers consider pasteurized
milk as safe. 1t should be required. if
the process be used. that il be heated
to a sufficiently high temperature to
kill with certainty all disease-pro-
ducing germs. Pasteurization GER
tainly necessitates better mode of
delivery of milk. but at best II is an
expedient rather than an ideal method
of dealing with milk No Trustworthy
conclusions can be drawn concerning
the effectiveness OF pasteurization
from the bacterial content of pasteur
lied milk sold in the retail market. as
one does not know the nature of the
milk before pasteurization. how long
IL has been kept. or the Temperature
at which IL has been kept; and I'm this
connection II must ever be remem.
bered that toxic products unaffected
by heat are constantly being produced
in milk. We have no method of deter
mining whether or. not pasteurized
milk was dsmaged before II was heat.
ed whereas the keeping quality and
bacterial content - raw milk furnish
good evidence of its real condition.