Why do we use a plate at bottom of a cooker?
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Food is cooked by the pressurized steam inside the pressure cooker. The steam is generated by boiling the water put inside the pressure cooker vessel. The weight valve releases the excess steam and maintains the pressure inside at a value higher than the atmospheric pressure.
The boiling point of water gets raised at higher pressures. The water inside the pressure cooker boils at about 115 degrees Celsius, a temperature higher than the boiling point, 100 degrees Celsius, under normal pressure conditions.
The boiling of water proceeds through the formation of steam bubbles at localized spots at the bottom of the cooker vessel.
It grows both in size and internal pressure before it gets detached and floats up to the surface where it bursts to release the steam into the vessel. The bubbles are often so large that they can partly lift and tilt the bowl containing the food ingredients of the dish to be cooked.
And this would occur at random locations, thus tilting and shaking the bowl rather violently. This can cause the ingredients, mostly water and some grains, to fall out of the bowl into the vessel.
Some times, more than one bowl is used for different dishes. In such occasions, they would get mixed up by the above processes. This is undesirable.
Such process of formation of large bubbles is prevented by arranging the bubbles to be released at small size itself. This is accomplished by the perforated plate.
When the bubble forms and grows in between the bottom of the vessel and the perforated plate, it tries to project out through the holes of the plate. The holes being small, the bubbles of small size get detached.
The plate has such holes at a large number of locations, and practically all the steam generated at the bottom of the pressure vessel is released as small bubbles at these holes.
These bubbles, being sufficiently small, are incapable of lifting the food bowl. This is how the use of the perforated plate prevents the above undesirable process.
The boiling point of water gets raised at higher pressures. The water inside the pressure cooker boils at about 115 degrees Celsius, a temperature higher than the boiling point, 100 degrees Celsius, under normal pressure conditions.
The boiling of water proceeds through the formation of steam bubbles at localized spots at the bottom of the cooker vessel.
It grows both in size and internal pressure before it gets detached and floats up to the surface where it bursts to release the steam into the vessel. The bubbles are often so large that they can partly lift and tilt the bowl containing the food ingredients of the dish to be cooked.
And this would occur at random locations, thus tilting and shaking the bowl rather violently. This can cause the ingredients, mostly water and some grains, to fall out of the bowl into the vessel.
Some times, more than one bowl is used for different dishes. In such occasions, they would get mixed up by the above processes. This is undesirable.
Such process of formation of large bubbles is prevented by arranging the bubbles to be released at small size itself. This is accomplished by the perforated plate.
When the bubble forms and grows in between the bottom of the vessel and the perforated plate, it tries to project out through the holes of the plate. The holes being small, the bubbles of small size get detached.
The plate has such holes at a large number of locations, and practically all the steam generated at the bottom of the pressure vessel is released as small bubbles at these holes.
These bubbles, being sufficiently small, are incapable of lifting the food bowl. This is how the use of the perforated plate prevents the above undesirable process.
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