Microwaves action on milk for infants

[Hans-Georg Klieber]

Stephane Corteel (scorteel at resulb.ulb.ac.be) wrote:
SC> ... warming up a feeding bottle using a microwave oven is not 
SC> recommended because the microwaves cause molecular changes in some 
SC> proteins of the milk.
 
  Heating of proteins (in general) causes denaturation. This means the
proteins loose their native structure which is a prerequisite for their
physiological function. Since we eat proteins only for the amino acids
of which proteins are assembled and into which they become dissasembled
by digestion this is (in general) not a problem. In fact the digestive
tract of adults is adapted to process denaturated (cooked, fried etc.) 
protein and we have problems with to much raw protein. Babies are
prepared to digest the "raw" ;-) mother milk by means of apropriate
enzymes.
  Depending on what kind of milk you feed to your baby a more or less
complete denaturation can be assumed anyway: fresh milk from the mother
(no denaturation) up to dry milk powder (complete denaturation).
 
hutchins at fiona.umsmed.edu (Jim Hutchins) wrote:
JH> ... Heating is heating, as far as proteins are concerned.
 
This certainly holds as far as the temperature itself is concerned.
But since heating in the microwave oven occurs through absorption of
radiation energy by specific chemical bonds and compounds of the 
material there is a possibility for direct effects on the molecular
level (radiolysis, similar to e.g. photolysis) besides the effects
of temperature. But I am not aware of any evidence for this!
(the microwave frequency should be tuned to affect mostly water
molecules, but any other chemical bond of similar resonance frequency
will respond)
 
JH> however ... Heating in the microwave tends to be uneven, ...
 
  I am shure, any considered mother will shake the milk bottle 
and check temperature and consistency of the food before offering
it to the baby. ;-)
 
  Besides this I see two points left:
  1) the uneven heating may locally heat up the milk to a temperature
far beyond the resulting average temperture. This could cause changes
to the milk proteins (and vitamins etc.) other than simple denaturation - 
but I do not have factual information on this.
(since the overheating would occur only in local hot spots it would 
probably not be limited to the boiling temperture of water)
  2) during a short time after birth (I do not know how long) the baby is 
able to take up antibodies (which are also proteins) which are in the
mother milk. These antibodies will of course loose their capabilities
if they become denaturated.
 
JH> ... placing the bottle in a hot water bath allows sufficient time for
JH> convection to occur and heating is, in general, more even.
 
If you decide to use a water bath: do not keep the milk unnecessarily
long heated! In warm milk the growth rate of any contaminating 
microorganisms (bacteria, fungi etc) is vastly accelerated - remember
milk is a very nutritious food!
 
It seems, introducing high tech to baby feeding raises some problems ;-)
Neverthless I hope you and your wife enjoy having a child!
 
Hans-Georg Klieber, Munich, Germany