Question

Freeze-dried foods have been dehydrated in a vacuum. During the process, the food freezes and must be heated to facilitate dehydration. Explain both how the vacuum speeds up dehydration and why the food freezes as a result.

a) Vacuum lowers the boiling point, freezing occurs due to reduced pressure.

b) Vacuum increases pressure, freezing occurs due to high pressure.

c) Vacuum decreases pressure, freezing occurs due to reduced temperature.

d) Vacuum has no effect on dehydration.

Answer 1

The vacuum speeds up dehydration by lowering atmospheric pressure and the food freezes due to the reduced temperature caused by the lower pressure.

Step-by-step explanation:

The vacuum speeds up dehydration in freeze-dried foods by lowering the atmospheric pressure, which in turn lowers the boiling point of water. When the food is placed in a vacuum chamber, the reduced atmospheric pressure causes the water molecules to evaporate more rapidly. This increased evaporation leads to faster dehydration of the food.

The food freezes during the freeze-drying process because the lower atmospheric pressure also reduces the temperature at which water can exist as a liquid. As the food is heated to facilitate dehydration, the water molecules freeze due to the reduced temperature. This freezing helps in preserving the food and inhibits the growth of bacteria or other microorganisms.