Pressure cooking is a method of cooking in a sealed vessel not permitting steam to escape below a preset pressure. Because the boiling point of water increases as the pressure increases, the pressure built up inside the cooker allows the liquid in the cooking pot to rise to a higher temperature before boiling.
The pressure cooker was invented by Denis Papin, a French physicist, in 1679. However, it only became a household cooking appliance during World War II, when the people realised how much fuel they could save due to the much shorter cooking time and the ability to cook cheaper cuts of meat easily. Pressure cooking is often used to simulate the effects of long braising or simmering in shorter periods of time.
Conventional pressure cookers were made to be used on stove top. A steam regulator, safety valve and pressure-activated interlock mechanism provide protection against overheating and the danger of explosion. When a pre-set pressure is reached in the cooker, the steam regulator is pushed up by the internal pressure to allow the steam to escape. This is the reason why the conventional oven top pressure cookers generate a loud and disturbing hissing noise when the pressure is on.
The Electric Pressure Cooker is an ingenious invention of the last decade. Historians are still undecided about inventors and the precise time. Arguably, a Chinese scientist, Mr. Yong-Guang Wang, filed the first electric pressure cooker patent on January 9th, 1991 (patent No. ZL91100026.7). This patent is currently owned by the No. 1 electric pressure cooker manufacturer, Midea.
An Electric Pressure Cooker consists of a pressure cooking container (inner pot or cooking pot), the electric heating element, and temperature / pressure sensors. The heating process is controlled by the built-in micro-processor based on the readings of the pressure and temperature sensors. This whole process forms a “closed loop control system” in control engineering terms. The principle is similar to that of cruise control found in many cars these days. The user puts all the ingredients in the cooking pot and sets the pressure cooking duration for the type of food to be cooked, the electric pressure cooker does the rest.
Over time, the leading electric pressure cookers learned from the experience and created different cooking profiles, such as simmering, steaming, braising, slow cooking, warming, rice cooking and stewing by using different combinations of cooking temperature, pressure and time duration. This has led to a new generation of electric pressure cooker, the programmable multi-cooker.
Read about how the electric pressure cooker works here.