Effective moisture diffusivity in biopolymer drops by regular regime theory

The effective moisture diffusivity coefficient (D-eff) of maltodextrin DE 10 (MD-10), gum arabic (GA), mesquite gum (MG) and ovalbumin (OA) drop solutions was calculated using regular regime theory. Isothermal drying of the biopolymer drops was done at 50, 60, 70 and 80 degreesC with a thermogravimetric analyzer, and changes in drop shape upon drying were followed with image analysis system. MD-10, GA and MG exhibited drop shrinkage upon drying described by second order polynomial, but OA did not. D-eff was dependent on moisture content and temperature. Activation energy (E-a) of the biopolymers was calculated from the slope of average effective diffusivity (D-eff) against temperature plots. E-a values exhibited by biopolymers drops from highest to lowest were: MD-10 (29.043 kJ/mol), MG (23.939 kJ/mol), GA (19.213 kJ/mol) and OA (7.487 kJ/mol). (C) 2003 Elsevier Ltd. All rights reserved.