1)
Batch pasteurization won't kill Johne's Disease.
In every
scientific study that we know of where batch
pasteurization was tested to see if it killed
Mycobacterium paratuberculosis (the bacteria
that causes Johne's Disease), the results
showed the bacteria was not completely killed.
It's believed that Johne's survived because
the milk is in a static state (non-turbulent)
during batch pasteurization. This allows the
bacteria to clump together, and while the
bacteria on the outside of the clump would
likely be killed, the ones near the center
of the clump could survive the heat. In a
study using flash pasteurization, where the
milk has a turbulent flow, Johne's was found
to be completely killed . The authors of this
study concluded "that turbulent flow
of milk during pasteurization is essential
for complete killing of contaminating"
Johne's bacteria.
2)
Batch pasteurization can increase the number
of bacteria in the milk.
Even
if Johne's is not a concern, batch pasteurization
is still not a good choice for calf milk.
The principle of batch pasteurization is to
heat a volume of milk to a minimum temperature
for a minimum amount of time. The most common
time-temperature relationship is 140°
F for 30 minutes. However, if all the milk
is not heated to the minimum temperature for
the minimum amount of time, bacteria that
may be present in the milk can be incubated.
This can result in a higher number of bacteria
then were originally present in the milk which,
when fed, can have a more detrimental effect
on the calves than unpasteurized milk. Because
of this problem of completely heating and
holding all the milk to the required temperature,
batch pasteurization is seldom used in the
dairy industry. Instead, flash pasteurization
is the dominant and preferred method of pasteurization.
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