Steaming is the cooking of prepared foods by steam (moist heat) under varying degrees of pressure. There are two methods of steaming: atmospheric or low pressure and high pressure. In low pressure steaming food may be cooked by direct or indirect contact with the steam. High pressure steaming takes place in purpose-built equipment, which does not allow the steam to escape, therefore enabling steam pressure to build up, increasing the temperature and reducing cooking time. The advantages are: retention of nutritional value; makes some foods lighter and easier to digest; low pressure steaming reduces risk of overcooking; high pressure steaming enables food to be cooked or reheated quickly because steam is forced through the food cooking it rapidly; and labour-saving and suitable for large-scale cookery.