Subtopic: Water activity, sorption and desorption isotherms
Question Statement:
In the moisture sorption isotherm hysteresis of dehydrated agricultural and dairy products, at any given constant water activity ($a_w$):
Options:
(A) The equilibrium moisture content on the desorption branch is always greater than that on the adsorption branch ($m_{\text{desorption}} > m_{\text{adsorption}}$)
(B) The equilibrium moisture content on the adsorption branch is always greater than on the desorption branch
(C) Both moisture contents are mathematically identical at all points
(D) Water activity is always exactly 1.0
Answer Key:
A
Step-by-Step Solution & Explanation
Due to ink-bottle capillary pore geometry, contact angle hysteresis, and structural shrinkage during drying, porous food tissues retain more moisture at a given water activity during desorption (drying) than during re-adsorption (wetting).