Question

At what stage the case hardening of a material takes place?

(a) Constant rate period

(b) Falling rate period

(c) Initial rate period

(d) Equilibrium

I have been asked this question by my college director while I was bunking the class.

Origin of the question is Drying Rate topic in chapter Drying of Food Processing Unit Operations

Answer 1

The correct option is (a) Constant rate period

The best explanation: The case hardening is defined as the formation of a hard skin on the surface of foods which slows down the drying rate and may leads to the mold growth. It is due to quick drying during the constant rate period and this can be stopped by using cooler drying air.