This is what human milk looks like when it’s been allowed to sit in the refrigerator for a few hours:
Notice that it looks layered. The top, opaque layer is cream. The bottom two layers are called milk plasma, or more commonly, skim milk. It is NOT recommended that you skim human milk before feeding it to an infant. You want to make sure your baby drinks the cream. The cream is chock-full of dense and vital nutrients to a developing baby, like cholesterol and fat, both of which are necessary for proper brain development. I would imagine that this is where most of the DHA found naturally in breast milk resides, too.
A lot of people recommend against shaking a container with breast milk in it, citing vague and slightly alarmist claims about “damaging the fragile milk components,” but I tend to think those people haven’t actually had to deal with preparing a bottle for a hungry, impatient baby. Also, I tend to think that while it’s not ideal to “damage the milk components,” shaking is also probably not nearly as “damaging” as it’s made out to be. The usual recommendation instead of shaking is “gentle swirling.”
“Gentle swirling” doesn’t always cut it in the real world. If you have the time, by all means, “swirl” away. But if your baby is hungry now and you’re faced with the dilemma of either giving the baby milk with less fat in it (because you’re afraid of shaking the milk and “gentle swirling” isn’t incorporating the fat stuck to the sides of the container) or shaking the container to get all the fat mixed well into the milk, well… Shake the container. It’s okay. Really. Obviously you don’t want to go overboard, because you don’t want to turn the cream into butter (unlikely, but it can happen… If you shake the container for about two hours), but you should harvest all the cream and get it back into the milk plasma however you can. Make sure your baby gets all the fat he/she needs to thrive. Note: It takes far less than two hours of shaking to accomplish this. More like 15 seconds.
Here’s a non sequitur that’s still about human milk:
What do you do with extra breastmilk that you don’t want to donate to anyone?
Make “momsicles!” This site shows you (with pictures!) how to cleverly make your own homemade teethers with mother’s milk. Awesome idea. I wish I’d thought of it myself. Although, even if I had, I don’t have any extra milk to spare for that… However, I could use yogurt as they suggest. Sounds like fun!