/learn/s29/t16219 /learn/node/56151 Bought milk has been processed to make it last longer (pasteurised) and remove some of the fat and make it more healthy (skimmed). /learn/node/56152 Milk changes when it goes sour, bacteria makes it curdle and sour to taste. Yoghurt and inkomaas are made when milk goes sour. /learn/node/56153 Cheese is made from processed milk; there are many different ways of making it. When cheese is heated it changes it’s properties. /learn/node/56154 Milk easily boils over when it is heated because it contains water and other nutrients such as protein and fat. When different ingredients such as egg and flour are added to a milk mixture and heated they help it to thicken.