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 curdThe 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…