At 09:18 AM 3/13/98 -0900, you wrote:
>Can someone provide a brief description of casein (what part of the milk
>is it)?
>
Hi Nancy,
Casein is a protein actually found in all parts of milk. There are 3 types
of casein, alpha, beta and kappa. They are found in different proportions
under different conditions. These proteins can float around freely by
themselves or form large structures called micelles. These micelles are
thought to look like a tennis ball with spikes or hairs poking out. The
fuzzy surface reflects light and gives milk its white color (fat particles
similarly reflect some). The spikes are kappa, the ball is mostly alpha and
beta tends to sit toward the centre. Addition of acid causes these hairs or
spikes to lay down flat and the ball can join up with another ball as in
yogurt. An enzyme can be used to chop these spikes off, allowing the balls
to bond into a network. This happens in cheese and is called the curd. The
watery remains is called whey. Whey contains a large amount of lactose once
the water (around 98%) is removed. There is some casein found but mostly 2
whey proteins. Whey is a waste product and is found dumped in all sorts of
food.
The casein proteins are also found on the surface of the fat particles.
This stabilises the fat globule and keeps it, or slows it seperating into
cream.

hope this helps

John