Thermodynamic sorption properties and glasstransition temperature of tamarind seed mucilage(Tamarindus indica L.)

Abstract

tAdsorption isotherms for spray-dried tamarind seed mucilage were determined at 20, 30and 40◦C and fitted to GAB and Caurie sorption models. The sorption properties were esti-mated using Kelvin and Helsey equations and the values found for the bound water were of15.98, 11.33 and 9.87% and specific surface areas of 142.29, 133.97 and 133.14 m2/g at 20, 30and 40◦C. The pore radius varied from 0.92 to 7.24 nm over the temperature range studied.The minimum integral entropy was observed at water activities of 0.11–0.21 and mois-ture contents between 2.17 and 2.29 kg H2O/100 kg d.s. Isokinetic theory suggested that theadsorption process was enthalpy driven. The glass transition temperature of the mucilagewas found between 46.4 and 79.7◦C. SEM micrographs showed that the mucilage at wateractivities less than 0.75 was in a glassy state and able to retain its morphology. Therefore,it was suggested that by relating minimum integral entropy, moisture sorption and glasstransition temperature in conjunction, it is feasible to extend the shelf-life of tamarindmucilage.