Food is cooked in a pressure cooker quickly because

The correct answer is Boiling point of water increases.

Key Points

•  A pressure cooker is a sealed container that traps steam generated from the boiling liquid inside, typically water or a water-based broth.
• As the liquid boils, the steam cannot escape, leading to a buildup of pressure inside the cooker.
• This increased pressure has a direct effect on the boiling point of water.
• The boiling point of a liquid is the temperature at which its vapor pressure equals the surrounding atmospheric pressure.1   
• In an open vessel, the surrounding pressure is the standard atmospheric pressure (approximately 101.3 kPa or 1 atmosphere).
• However, inside a pressure cooker, the trapped steam increases the pressure above the liquid's surface.
• According to the Clausius-Clapeyron relation, the boiling point of a liquid increases with increasing pressure.
• Therefore, in a pressure cooker, water boils at a temperature significantly higher than its normal boiling point of 100°C (212°F).
• This higher boiling point means that the food inside the pressure cooker is cooked at a higher temperature.
• The rate of chemical reactions, including the cooking of food, generally increases with temperature.
• For every 10°C (18°F) increase in temperature, the rate of many chemical reactions approximately doubles.
• Consequently, cooking food at the elevated temperatures achieved in a pressure cooker significantly reduces the cooking time.
• The higher pressure also helps to force moisture into the food, which can contribute to faster and more even cooking.
• While a pressure cooker is designed to retain heat efficiently due to its sealed nature and typically thick walls, the primary reason for faster cooking is the increased boiling point of water.