How to make cheese?
The transformation of milk into cheese is one of the brilliant achievements of humankind. It enables us to take a product that spoils fast at ambient temperature (milk), and makes a product that lasts (cheese). Technically, some cheeses could last forever.
Milk is comprised of about 87% water. The object of cheese making is to turn milk into a solid by removing some of this water and acidifying the milk – the amount to be removed depending on how long you want the cheese to last. Drier (and thus, harder) cheeses keep fresh longer.
Setting milk into curd
The first step to removing the excess water is by separating the milk into curd and whey. To set the milk into curd, it is gently heated, and then cultures (called ‘starter cultures’) and rennet are added. The cultures added are lactic-acid-forming bacteria that change the lactose (sugar) in milk into lactic acid; this chemical change prompts the milk to curdle (you’ll see this curdling if you let milk go off at home). In order to assist with this process, an enzyme, rennet, is also added. Rennet joins up the proteins in the milk to allow the milk fully to coagulate and form the curd (a firm jelly-like substance).
Altering the amount of rennet, the speed of the set, and the nature of the acidification of the milk by the starter bacteria (its speed and the final level of acidity) are all factors that will determine what style of cheese will be created before it is matured.
Separating the curds and whey
Once the curd is set it is cut into small pieces. This is done using knives, wires, or by ladling. The cutting allows even more whey (mainly water) to be released from the solid curd. The smaller cut the pieces, the more whey is released, the drier the curd, and the harder the final cheese.
Moulding and salting the curd
The curd and whey can also be heated and the curd stacked afterwards to encourage further separation, before the curds eventually settle and the whey can be fully drained off.
Once the whey is removed, the curd is broken up, salt is often added (for flavour, as a preservative and to inhibit growth of certain bacteria), and the cut curd is placed into moulds.
Pressing the curd
Often the curd is then pressed, to push and squash the particles together, forming a hom*ogeneous texture in the final cheese, and removing the last bits of whey. After pressing (often for a few days), the cheeses are removed from the moulds, cloth-bound (for traditional British cheese) and taken to a cool, humid store to mature for between 1 and 15 months, and sometimes longer…
Different Cheese Types
By tweaking the above stepsand introducing different cultures you can then obtain a vast range of cheese types. The diagram below gives a simplified version of how that is achieved:
For more information on cheesemaking, and further detail on how we get such a diversity of cheeses from tweaking these steps, check out one of the blogs below.
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