PRESSURE COOKING

 QUESTION 

Why is food cooked quickly in a pressure cooker ?

Boiling:

 The process in which a liquid changes into gaseous state at a constant temperature and pressure is called boiling. 

Example: water boils at 100°C to change into steam.

Boiling  point:

The temperature at which boiling takes place at a given pressure is called boiling point. 

Example: The boiling point of water is 100°C. 

Boiling of  a liquid starts when the vapour pressure of the liquid heated is equal to the air pressure above the liquid surface. If we can increase the pressure above the liquid surface then boiling is  delayed and hence the boiling point is increased. 

So, when steam is retained inside the cooker, boiling point of the liquid increases to 120-125°C.

As the food is cooked at higher temperature in the pressure vessel, it is cooked easily and quickly.