Cheesemaking is a complex science – a food chemist explains the process from milk to mozzarella Hundreds of different varieties of cow’s milk cheese are made across the globe, and they all start with milkCheese is a relatively simple food. All cheesemakers first pump milk into a cheese vat and add a special enzyme called rennet. Cheesemakers salt other cheeses, like mozzarella, by placing them in a salt solution called a brine. Historically, cheesemakers used raw milk, and the bacteria in the raw milk soured the cheese. In some types of cheese, these cultures stay active in the cheese long after it leaves the cheese vat.