Empirical Model for Water Uptake and Hydration Rate of Food Powders by Sorption and Baumann Methods

The empirical model q = Q t/B + t, where q is the amount of water taken up at time t was useful to describe water uptake of several food powders determined either by the Baumann or the sorption isotherm method at 75.6 and 100% RH. The equilibrium values (Q) and the specific rate constant (K) derived from this model as (QB)^-1 could be used to characterize food materials for hydration capacity and rate. Large differences were observed in Q values between methods and between food powders. The Baumann Q values and sorption isotherm Q values at 100% RH ranked similarly water takeup of food powders (R = 0.97, p < 0.001). Baumann K values and sorption isotherm K values at 100% RH also correlated highly. However, little differences were observed among the K and Q values of different food powders determined by the sorption isotherm method at 75.6% RH.