Estimation of the activation energy of carbohydrate polymers blends as selection criteria for their use as wall material for spray-dried microcapsules

A quantitative method for selecting the most suitable biopolymers blends for lipid materials microencapsulation is proposed. Aqueous solutions of carbohydrate polymers blends (gum arabic (GA), mesquite gum (MG) and maltodextrin DE 10 (MD)) were prepared in accordance to a Simplex Centroid experimental design, and a drop of each blend was dried isothermally at 50, 60 and 80degreesC in a thermogravimetric analyzer. The effective diffusivity was dependent on moisture content, drop volume shrinkage, and temperature. Drop shrinkage was estimated from polynomial models reported for GA, MG and MD, assuming additive volumes of the blend constituents. Activation energies were calculated considering that the average effective diffusivity followed an Arrhenius-type relationship. The pure biopolymer exhibiting the highest activation energy was MD, followed by MG and GA, respectively. Blends containing 66%GA-17%MG-7%MD and 17%GA-66%MG-17%MD showed higher activation energies than MD, MG and GA suggesting that they better suited for protecting microencapsulated lipids against oxidation. (C) 2003 Elsevier Science Ltd. All rights reserved.