How do you make cheese?

Last week in Sisters4Science at Reavis, we learned about food science with our guest scientist Daina!

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First, the Sisters shared what they knew about cow milk–Aaliyah remembered that it had proteins and vitamins in it, and we also discovered that milk has lactose, which makes milk sweet.
Each Sister tasted two different types of Greek yogurt, a piece of mozzarella cheese, and a piece of parmesan from Wisconsin. We found that one type of yogurt was more sour than the other; the mozzarella didn’t have a very strong taste; but the parmesan was harder than the rest, and sort of tangy or nutty. Even though all of these foods were made from cow milk, they were all made in different ways, which is why they look and taste so different!
With some styrofoam models, we discovered that milk molecules have structures called “casein micelles,” which keep the molecules far apart and the milk liquid. By using acid or an enzyme called rennet, we can break these up and allow the molecules to come closer together to make something solid (like cheese!).
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So, we tried it out! Each Sister added acidic lemon juice to milk, and then filtered it to get the whey out. We also tried adding rennet to milk, and it become much more solid. To test the acidity of each mixture, we used red cabbage, which changes color based on pH. We saw that the whey we made was more acidic than the milk, which was more acidic than water. We learned a lot, and had the opportunity to try some new foods too! Great job, Sisters!
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