Pressure cooking is the process of cooking food, using water or other cooking liquid, in a sealed vessel known as a pressure cooker, which does not permit air or liquids to escape below a pre-set pressure. Pressure cookers are used for cooking food more quickly than conventional cooking methods, which also saves energy.
Pressure cookers heat food quickly because the internal steam pressure from the boiling liquid causes saturated steam to bombard and permeate the food. Thus, higher temperature water vapour, which transfers heat more rapidly compared to dry air, cooks food very quickly.
Pressure is created initially by boiling a liquid such as water or broth inside the closed pressure cooker. The trapped steam increases the internal pressure and temperature. After use, the pressure is slowly released so that the vessel can be safely opened.
Pressure cooking can be used to quickly simulate the effects of long braising or simmering. Almost any food which can be cooked in steam or water-based liquids can be cooked in a pressure cooker.