The liquid which is left from churning the cream which has been used in butter-making, buttermilk consists of about 90 per cent water, 5 per cent milk sugar, 3
per cent casein, or milk protein, mineral salts and lactic acid, which gives it a sour taste. Buttermilk is used with
bicarbonate of soda as a raising agent, in the proportion of 10 fluid ounces of buttermilk to
½ teaspoon of soda. Commercial buttermilk is available in cartons and is widely used in recipes, especially in the United States. It also makes a nourishing and refreshing drink.