When you think of milk, you think of a creamy liquid. For tonight’s MEL Science experiment, Najwa was going to separate the liquid from the solid part of milk, the curd.
This was similar to the project we did over the summer when we poured milk into Coke. The phosphoric acid in the Coke attached to the protein clots in the milk, making them settle at the bottom, leaving behind a clear liquid. In this experiment, we’re going skip the Coke and make the milk the clear liquid this time.
So first, we needed some milk. Whole milk might be better, but we don’t do whole milk. I don’t do milk at all because of another chemical reaction that takes place in my gut.
Milk consists of water with tiny drops of fat and protein clots that are both suspended in it. As long as the protein clots are small enough, they can float freely. When you drink milk, you don’t even realize there’s these little drops of fat and protein clots. We added a little calcium chloride CaCl2 to coagulate the liquid.
Next, we fired up a few tealight candles to heat up the milk for a few minutes.
Anyone who has heated milk in a recipe already knows what happens. The clots become too big to be suspended in the liquid, clump up, and make you wonder why you even drink the stuff. To separate the clots, or curd, from the liquid, we poured the mixture into a Erlenmeyer flask through filter paper.
And there you have it. What was milk is now filter paper full of curd and flask with what’s essentially water.
Najwa didn’t want to stop there, though. She wanted to put the curd back into the liquid to make milk again. But it doesn’t work like that. The milk went through a chemical change, hence it’s a chemistry project, rather than a physical change. It’ll make more sense when she reaches whatever grade they learn those things.