Basics of cheese making
The main two things that you need to know about the science of cheesemaking are that there are two main proteins that are relevant—casein and whey (whey is actually a group of several proteins, but collectively calling them all “whey proteins” will suffice for now). Although it plays a role in determining the firmness of cheese, whey is generally considered a waste product in cheesemaking. Casein is the main protein component of cheese.
Casein is actually a micelle composed of four subunits, called α-s1, α-s2, β, and κ (pronounced alpha s1, alpha s2, beta, and kappa). α-s1, α-s2, and β are hydrophobic and stay in the interior of the micelle. κ- casein, however, has both a hydrophobic and hydrophilic portion, and can interact with both the hydrophobic proteins of the micelle interior, and with the aqueous solution that is milk. Therefore, it coats the outside of the micelles, with its hydrophobic portion pointing inward, and its hydrophilic portion (its “tail”) projecting out into the aqueous phase.
This hydrophilic property of κ- casein is what allows the micelles, which would otherwise be hydrophobic, to be dissolved and dispersed in the aqueous medium (i.e. milk).
To make cheese, however, we need to make casein insoluble in water. Thus, κ-casein must be made hydrophobic, and there are two main ways to do this:
One way is to cleave off the hydrophilic “tail” portion of κ-casein with the enzyme chymosin (traditionally derived from the stomachs of calves as part of a mixture called “rennet,” but now more commonly produced in genetically engineered bacteria).
The other way is to neutralize the negatively charged amino acids on the hydrophilic portion of κ-casein using acid. Either way, the result is a micelle which has a (nearly) net neutral charge, therefore making it hydrophobic, and insoluble in water. The insoluble globs are what are known as curds, and the remaining liquid is what is known as whey.
For soft cheeses like cottage cheese, queso fresco, and cream cheese, the work is mostly done—the curds are simply collected. These cheeses are usually made by acidification.
For harder cheeses like cheddar, Swiss, and parmesan, the collected curds are cut and pressed to remove even more of the liquid. These cheeses are typically made using chymosin.
The video at the following link explains this very well.
Here is another video by RVC’s own Ben Rupert that I found extremely helpful when I was learning the basics of cheese science: