Question

At what point the ice crystal formation takes place?

(a) When the material is cooled below itstriple point

(b) When the material is cooled below its freezing point

(c) When the material is cooled below its dew point

(d) When the material is cooled above its triple point

This question was posed to me in homework.

The above asked question is from Freeze Drying topic in chapter Drying of Food Processing Unit Operations

Answer 1

The correct choice is (a) When the material is cooled below itstriple point

To explain: During the freezing stage, the product is cooled below its triple point, this is achieved to ensure that melting does not takes place. Triple point is the lowest temperature at which the liquid, solid and gas stages of the material can coexist.