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I Made Cheese!

When I started this blog, I wanted it to be a about science and pedagogy. When I look at what I've written so far, it's all pedagogy. So, now it's time to bring on the SCIENCE! This is the science of making mozzarella cheese. Or, at the very least, the science of the ingredients.

Here's what I needed to make the cheese:

  • Milk
  • Salt
  • Rennet
  • Citric Acid
  • Water
Here's what I learned about the science behind the ingredients. 

Milk: Any milk will do as long as it isn't ultra high temperature pasteurized (UHT). Apparently, if the milk is ultra high temperature pasteurized, the heat may cause the proteins to denature, or lose their shape. When proteins denature they are not able to function appropriately. If this happens they will not be able to come together to form curds. When milk is UHT pasteurized it is heated to 280 degrees. That't pretty hot for the proteins in milk. And while I would want the proteins to denature if I was making yogurt, I definitely don't want it to happen in my cheese making milk.

Milk is composed of 3.3% protein. Of that, 82% is casein and the other 18% is serum or whey protein.  The whey protein is more heat sensitive and may be denatured by UHT pasteurization. This process is commonly used in organic milk. So, I spent the days before the cheese making obsessing about the milk and emailing the milk producers. No one emailed me back to I just went for it with some *gasp* non-organic, full fat milk!

Salt: Just makes things yummier. Also, did you every wonder why salt has an expiration date? How can a mineral expire? It seems as though if you have iodized salt, it typically has a self life of 5 years but regular old salt will last you forever.

Salt, also know as halite, has a chemical formula of NaCl (one atom of sodium bonded to one atom of chlorine). Fun fact, the concentration of salt in your cells is very similar to the concentration of salt in ocean water. Coincidence? Things that make you go Hmm....

Rennet: So, what is rennet anyway? Get ready for some ewww.....Rennet is made from enzymes that are produced in the stomachs of ruminant animals (these are animals like giraffe, cattle and sheep that chew their own regurgitated cud. Sounds delicious). The main enzyme in rennet, chymosin, helps young mammals digest their mother's milk. But, good news! There is vegetarian rennet. Vegetable rennet is made from the chymosin produced by mold. Seems as though cheese and mold are always finding their way together.

Rennet is used in cheese making to separate the cheese curds (the proteins) from whey (liquid component of the milk). When rennet is added to the milk, the proteins coagulate forming the curds that are used to make the cheese.  They can then be removed and processed into cheese.

Citric Acid: Citric Acid is a fairly weak acid that causes the protein casein in the milk to coagulate. But citric acid pulls double duty in the cheesemaking process.  The citric acid also serves to lower the pH of the milk to around 6. This is the optimal pH for the rennet to do its work. Cheese that is produced without acidification usually has significantly lower yields of final product.

Throughout the process the cheese is heated to speed up the curdling process and help in shaping and kneading.

So, in the end, I followed all the directions, thought scientifically about all the directions and made some fairly decent cheese. It was a little rubbery because, I think, I kneaded it too much. But now I know for next time!

PS - I made cheese again this weekend. This time I kneaded it a little less. The consistency was better but the taste was a little to citric acidy for my taste. So, the experimentation will continue.



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