Step 2: Milk

As a biological product, milk contains proteins, the principal milk proteins are known as casein but it also contains other proteins. It consists of 80% casein and 20% whey protein. There are four major types of casein molecules: alpha-sl, alpha-s2, beta, and kappa

Because of the negative charge of the casein, it is dispersed in milk so if we want to make cheese we need to denaturate casein to coagulate it.

Denaturation of milk proteins
When an acid is added to milk, the H+ concentration neutralizes the negatively charged casein micelles. When milk is acidified to pH 4.7, it reaches its isoelectric point (the point at which all charges are neutral) and it forms a precipitate known as acid casein. Cottage cheese and cream cheese manufacture involves an acid precipitation of casein with lactic acid or lactic acid-producing microorganisms. Acid casein is used in the chemical industry and as a glazing additive in paper manufacturing.

Casein also can be coagulated with the enzyme rennin, which is found in rennet (an extract from the stomach of calves)
Do you remember which factors affects proteins? If not, go back to step 1 because rennin as a protein is affected by these factors and is enzymatic activity can change.
Rennin works best at body temperature (37 C). If the milk is too cold, the reaction is very slow, and if the milk is too hot, the heat will denature the rennin, rendering it inactive. The mechanism for the coagulation of the casein by the rennin is different from the acid precipitation of casein. The coagulation of the casein by rennin is a two-stage process. In the first stage, rennin (a proteolytic enzyme which means it acts only on proteins) splits a specific bond in the amino acid chain of the kappa-casein macromolecule converting it into a-para-kappa-casein and a glyco-macropeptide. This causes an imbalance in the intermolecular forces in the milk system, and the hydrophilic (water-loving) macropeptides are released into the whey. Unlike kappa-casein, the parakappa-casein does not have the ability to stabilize the micellular structure to prevent the calcium-insoluble caseins from coagulation. In the second stage, colloidal calcium phosphate (this is and example of other compound affecting proteins) bridges within the casein micellular structure, resulting in the three-dimensional curd structure.
The rennin coagulum consists of casein, whey protein, fat, lactose, and the minerals of the milk, and has a fluffier and spongier texture than the acid precipitate. Rennet is used in the manufacture of cheese and cheese products (nowadays, most of the cheese producers do not use calve rennet because is very expensive they use "vegetable rennet" which is made from microorganisms), and rennet casein is used in the plastics industry.
This molds after a while. :P <br>
I really enjoyed the quality of your instructable; you put in so many pedagogical aids...infographics, glossary, multiple well selected photos on and on. Question; how does pastuerization reduce the calcium content of milk as you state in Step 7?
wonderful instructable, thank you for posting.
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do you have to have remmet and calcium chloride? can u use somthing else
heat the milk till it's near boiling and add lemon. kill the flame and cover for 30 minutes, cut up the curds and continue with step 10
Great 'ible. I've been reading about the health benefits of whey protein (claims for muscle building/maintaining, insulin regulation, etc.) Instead of, or in addition to, ricotta, could the whey liquid be processed into a "sports drink"? How much protein would it contain?
Thank you for the instructable! Quick question: Where can I find calcium chloride locally? I know it's available online, but where can I go pick it up in a store? I live in Northern California, of course, my town probably looks very much like your town. Your anticipated wisdom and knowledge is greatly appreciated! :)
I got my liquid calcium chloride, natural rennet and vegetarian rennet from <a rel="nofollow" href="http://www.cheesemaking.com/">http://www.cheesemaking.com/</a><br/>
here's a source of calcium chloride and other things<br/><a rel="nofollow" href="http://glengarrycheesemaking.on.ca/index.htm">http://glengarrycheesemaking.on.ca/index.htm</a><br/>
An amazing job- I especially like the use of a glossary for individuals like myself that are a bit lacking in the necessary knowledge base. :P
That was an intense tutorial! I'll have to try it.<br/><br/>Check <a rel="nofollow" href="http://www.instructables.com/id/EN6AXM0YAOEV2Z6A2R/">here</a> for info on inserting clean-looking links.<br/>
Thank you, now the links look is better

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Bio: Food Chemist with a desire to study Entomology some day. Hobbies: Cooking, origami, reading, watching anime, my crazy pigeon and sometimes videogames.
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