Sorption isotherms of powdered cajá-manga pulp in different drying processes

Abstract

ABSTRACT High-sugar dehydrated foods have strong hygroscopicity, which can be avoided by using drying aids. One way to assess the hygroscopic behavior is through sorption isotherms. The objective of this work was to evaluate the influence of maltodextrin concentration on sorption isotherms of powdered cajá-manga pulp in spray-dryer, lyophilization and fluidized bed spray drying processes. The dryings were carried out in a spray-dryer, lyophilizer and fluidized bed, with 10%, 20% and 30% of maltodextrin. Adsorption isotherms were determined by the static gravimetric method using salt solutions for a relative humidity range of 21% to 90%. The GAB, BET, Henderson, and Oswin models were adequate to the experimental data. The relative deviation between the experimental values and the estimated values was calculated for each curve, in order to assess which equation best fit the experimental data. The mean relative error value of less than 10% was considered one of the criteria for selecting the models. The BET (A), BET (B) and GAB (C) models had the lowest error means, 3.35%, 3.35% and 5.28%, for cajá-manga powders obtained by spray-dryer, lyophilization and fluidized bed spray drying processes, respectively, and coefficients of determination above 0.99. It is concluded that the type of drying process did not influence the behavior of the adsorption isotherms, and that increases in maltodextrin concentration and temperature are significant in reducing equilibrium moisture contents.

Keywords

• Equilibrium curves
• Dehydration
• Isotherm models
• Cajarana