The science behind freeze drying

The four stagesread the section about the four stages.

The triple point of a substance is the pressure and temperature that solid, liquid, and gas can exist at the same time (in equilibrium).

Sublimation is when a substance passes from a solid to a gas. Sublimation can be sped up by cooling a substance and placing it in a vacuum to bring its temperature and pressure below the triple point. When the temperature is increased with the vacuum, the phase shift is from a solid to a gas.

Freeze drying can reduce the moisture composition of food down to between 1-4%.

Changes that happen during freeze drying

Physical changes:

  1. Freeze speed can affect the cell walls of the material — results in a “mushier” reconstituted product
  2. Some foods will brown, or otherwise change in appearance — e.g. carrots lose some of their orange color
  3. The obvious benefit: water content and mass decrease

Chemical changes:

Not much for chemical changes, thus the benefit to freeze drying.


Read our most recent blog posts about freeze drying :