Sour milk cheese is a cheese that has been curdled (coagulated) by natural souring or by the addition of lactic acid bacteria, such as cottage cheese. Sour milk cheese does not use rennet for coagulation. Sour milk cheese generally ripens for no more than two weeks in comparative warmth. 100 litres of milk yield about 8 to 9 kilograms of sour milk cheese[citation needed], which contains less than 10% fat and up to 37% protein. Most sour milk cheeses are white mould cheeses or red mould cheeses, and many are flavoured with caraway. The various types of sour milk cheeses include: