After milk coagulation the newly formed curd is cut in order to initiate moisture loss.
As we’ve discussed before, a cheesemaker is charged with the task of transforming liquid milk into solid cheese. That solidification process is known as coagulation. From there, the curd mass is cut, moisture is lost, protein and fat are concentrated to form the cheese body. It’d be a good idea to review the coagulation post before continuing here.
Cutting the coagulated curd mass (also called the coagulum) initiates the moisture loss from the soon-to-be cheese. This moisture loss is known as whey expulsion and is an example of syneresis. A way to think about this is like cutting through a sponge. But cutting the curd mass, the cheesemaker is exposing all the tiny gaps in the “sponge” allowing whey/water to leak out. The amount of moisture that will be lost from the cut surface is a function of the surface area of the newly formed curd particles.
All else being equal, cutting smaller curds will lead to more moisture loss, and larger curds lead to less moisture loss. This is due to smaller pieces having a greater surface area-to-volume ratio. Simply put, cutting the curd into smaller pieces will lead to drier cheeses. For example, Grana-style cheeses like Parmigiano-Reggiano start off with small rice-sized curd particles. Higher moisture cheeses like Brie will be on the other end of the spectrum with larger curd particle size. After cutting, the curds are usually allowed to rest. This is called the “healing” step. After this the curds are usually “cooked”. They are heated and stirred resulting in even more moisture loss. See the Grainy Grana post for more information.
In order to accomplish the cutting process a cheesemaker will use something called a cheese “harp” or cheese “knives”. These devices are made up of parallel knife blades and/or wires. The cheesemaker will insert the harp/knives into the vat of cheese and then draw them along the curd mass. This process is usually repeated in several directions in order to form curd cubes. This process can also be automated by using motorized knives, which is more common in larger-scale operations. While using knives to cut the curd is popular, in some cases there isn’t a need to actually “cut” anything. For some cheeses, like ricotta for example, simply stirring the coagulated milk is enough to break up the curd particles.
For More Information
- Encyclopedia of Dairy Sciences - Curd Syneresis
- Cheese: Chemistry, Physics and Microbiology - The Syneresis of Curd