This is from a test performed in Norway by members of the Professional
Council on Breastfeeding.  There are two graphs accompanying the article and
I can send the graphs to anyone who mails me privately as I must send them
as an attachment, a Word-document.

The most important conclusion is that the use of microwave ovens to thaw
milk causes a nearly complete loss of antibacterial qualities in breast
milk.  The next most important is that even freezing and thawing the breast
milk twice doesn't appreciably shorten the 'shelf life' of this high quality
food.  It seems that fresh or properly treated (see below) frozen breast
milk may be held at least five times longer (and possibly more) than one
could safely hold artificial milk or pasteurized cow's milk.  Read on for a
short description of the procedure.  The report I have doesn't give exact
amounts but the graphs are easy to understand.

First, they inoculated a known amount of E. coli into culture medium, and
into samples of freshly expressed milk, pasteurised whole cow's milk from a
carton purchased at a grocer's, and industrially produced artificial baby
milk.  These cultures were incubated for three and a half hours at 37
degrees C (body temp) after which time samples were withdrawn from each
container and bacterial counts done.  The relative quantities of bacteria
were expressed in terms of the count for the bacterial culture medium which
was set to one.  Freshly expressed breast milk had a count of less than 10%
of the culture medium.  Cow's milk had 3 times the amount of the culture
medium.  Artificial baby milk had 2.5 times the amount of the culture
medium.
Next, they tried the same procedure using freshly expressed breast milk, and
milk which had been frozen and then thawed by four different methods: left
to stand at room temperature (around 20 degrees C); a 40 degrees C water
bath; the thawing program of a microwave oven; and finally a sample which
had TWICE been deep frozen and then thawed to room temperature.  Compared to
the bacterial growth in culture medium, the fresh milk and the milk thawed
at room temperature had about 10% as much bacteria.  The milk thawed in a
hot water bath had about 20% as much bacteria as culture medium.  The same
was true of the twice frozen/twice thawed at room temp sample.
The sample thawed in the microwave had four times the bacterial count of the
culture medium-- a third more than the cow's milk from a carton.

Rachel Myr

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