Question

What drying method makes use of the fact that for each solvent in a closed container there

is a temperature and pressure at which vapor and liquid densities are equal?
A) air drying
B) critical-point drying
C) forced air drying
D) vacuum drying
E) dehydrational drying

Answer 1

Freeze-drying foods involves utilizing a vacuum to decrease atmospheric pressure, thus enhancing evaporation and causing the temperature of the food to drop and freeze. Subsequent heating facilitates sublimation, preserving the food's original quality.

Step-by-step explanation:

The freeze-drying process, also known as lyophilization, is used to dry foods by placing them in a vacuum chamber. This method utilizes a vacuum to decrease atmospheric pressure, which consequently decreases the partial pressure of water and the humidity, leading to enhanced evaporation of water from the food. The energy required for some water molecules to evaporate comes from the remaining water molecules, which lose kinetic energy and decrease in temperature, often resulting in the food freezing.

As humidity is lower under reduced pressure, water molecules are more likely to sublime directly from a solid to a gas, which speeds up the drying process. The food must then be heated in the vacuum to facilitate the sublimation. The resulting dried product preserves much of the food's original texture, nutrients, and flavor, making freeze-drying an advantageous method for food preservation.