Hi everyone, Julie from Savvy Eats here!  For those of you who are unfamiliar with my blog, I am a Food Science & Engineering student at the University of Wisconsin-Madison, graduating in May. I’m an unusual engineering student in that I don’t want to do super-technical work when I graduate. What I really want to do is write about food. More specifically, I’d like to write about the science behind food.  To that end, I am starting a new series this week on my blog answering all your food science questions!

For my guest post today, then, I thought I’d explain why yogurt is a good source of calcium, but cottage cheese is not.  Hey, I live in Wisconsin, aka Dairyland, so it is entirely appropriate for my first post!

First of all, whole milk is essentially a bunch of fat molecules trapped in a water-based fluid.  The only reason that the fat and water don’t separate is that the proteins in milk keep it from doing so.

There are two types of proteins in milk.  Most of the proteins are casein, which are not soluble in water, but about 20% are whey proteins, which can dissolve in water.

That is the important part to keep in mind.

Whey = Soluble in water.  The green-ish liquid in the picture below, from food-info.net.

Casein = Not a fan of water.  Not water-soluble and therefore steers clear of it as much as possible.  Oh, and all the calcium is naturally found in the casein, not the whey!

Cottage Cheese

To make cottage cheese, the casein must be separated from the whey.   When this happens, the calcium leeches out of the casein and into the whey proteins.  Since all of the casein and only a little of the whey is curdled to make cottage cheese, then, there is very little calcium.

To summarize

Whey = Now has the calcium, and isn’t in cottage cheese.
Casein = Becomes cottage cheese, but has lost its calcium to whey.

Yogurt

To make yogurt, both the casein and whey proteins are curdled together, so none of the calcium leeches out.  Yogurt, then, is a great calcium source!

Yogurt = Contains casein + whey, and therefore keeps the calcium!

I hope you have found this interesting and enjoyable.  I’ll be posting soon on savvyeat.com about why you can use a flax/water mixture in the place of eggs when baking.   I hope you’ll check it out!

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