Asian Journal of Applied Chemistry Research

The objective of the present work was to investigate the sorption isotherms of moisture in spray dried microcapsules powder of X. americana at 25°C, 35°C and 45°C temperatures. A gravimetric storage study of spray dried microcapsules of Ximenia americana fruit extracts was conducted for 0.22 to 0.93 water activity (a_w) at 25°C, 35°C, and 45°C. The net isosteric heat (q_st) of water adsorption was calculated using the Clausius–Clapeyron equation. Experimental data were fitted to mathematical models developed by GAB, BET and Peleg, since R² was close to 1 for the investigated conditions. It resulted that the moisture content of spray dried microcapsules of X. americana fruit extracts had an increasing trend by increasing of a_w value, and these microcapsules adsorbed 55-65 g H₂O/100 g solid. The adsorption isotherm of spray dried microcapsules of X. americana detected as Type II according to Branuer classification. The monolayer moisture contents (X_m) of microcapsules formulated were determined as 8.14-9.67 g H₂O/100g solid according to GAB and BET equations. Lower moisture concentrations caused a more drop in isosteric heat, after which there was no further change. The results of this study therefore suggest that for a long and high-quality storage of whole spray dried microcapsules powders of X. americana fruits extracts, the relative humidity should be lowered to 35 g/100g.