The operation of a pressure cooker is based on the Clausius-Clapeyron equation, which establishes that a liquid's boiling point is directly proportional to the pressure exerted upon it. At standard atmospheric pressure (101.3 kPa), water boils at 100°C; however, when the pressure rises to 150 kPa, the boiling point increases to 111°C, allowing cooking times to be reduced by 30% to 50%. For instance, stewing beef brisket takes two hours in a conventional pot but only 40 minutes in a pressure cooker, while the time required to cook dried beans drops from three hours to one hour. This increased efficiency not only saves energy but also minimizes the loss of water-soluble nutrients, such as Vitamin C.
Pressure control technologies fall into two categories: mechanical and electronic. Mechanical systems regulate pressure by adjusting the weight of the lid assembly (weighted valves) or spring tension (spring valves); while cost-effective, they offer limited precision (±5 kPa). In contrast, electronic systems utilize pressure sensors and microprocessors to achieve precise pressure control (±1 kPa) and support various preset cooking modes (such as rice cooking, meat stewing, and soup making). Some high-end models also feature intelligent pressure release functions that automatically and gradually vent pressure after cooking concludes, preventing ingredients from rupturing due to sudden decompression (such as eggshells cracking during boiling).
