Subtopic: Water activity, sorption and desorption isotherms
Question Statement:
Water activity ($a_w$) of a food material at equilibrium is thermodynamically defined as the ratio of:
Options:
(A) Vapor pressure of water in food ($p$) to vapor pressure of pure water ($p_0$) at the same temperature
(B) Moisture content dry basis to moisture content wet basis
(C) Mass of bound water to mass of free water
(D) Enthalpy of desorption to latent heat of vaporization
Answer Key:
A
Step-by-Step Solution & Explanation
Water activity is defined as $a_w = \frac{p}{p_0} = \frac{\text{Equilibrium Relative Humidity (ERH)}}{100}$, representing the chemical potential of water in the food matrix.