Effect of temperature and hysteresis on Monolayer moisture content of Moringa see Grit during storage

Abstract

The adsorption and desorption isotherm data of stored moringa (Moringa oleifera) seed grit within the water activity and temperature ranges of 0.09–0.92 and 20–40oC respectively were used to determine its monolayer moisture content (Mo) using the Brunauer-Emmett-Teller (BET), Guggenheim-Anderson-DeBoer (GAB) and Caurie equations. Results showed that Mo decreased from 3.03 to 2.064 %db (BET); 4.38 to 2.792 %db (GAB); 4.24 to 2.63 %db (Caurie) and 3.007 to 2.011 %db (BET); 4.346 to 2.621 %db (GAB); 4.215 to 2.545 % (Caurie) in adsorption and desorption processes respectively as temperature increases from 20–40oC at specified relative humidity. The GAB model gave the highest Mo values at various temperatures followed by Caurie equation while the BET model gave the lowest values. The Mo were lower in desorption process than the corresponding adsorption values for the three models, thereby indicating the presence of moisture sorption hysteresis. However, one way analysis of variance (ANOVA) showed that there were no significant differences between adsorption and desorption Mo at (p≤0.05), thereby indicating that moisture hysteresis has a negligible effect on the monolayer moisture content of moringa seed grit.