Vacuum Radiant Energy Drying Kinetics of Alginate Gel

Abstract

Radiant energy drying under vacuum was investigated for hydrogel produced by mixingsodium alginate, high methoxy pectin and corn starch in which sodium alginate acted as a gellingagent in the presence of calcium chloride. Glycerol was used as a plasticizer. Drying was conductedusing 2450 MHz microwave energy at different power levels viz., 300, 500, 700, 900 and 1100 watts.For all the power levels absolute chamber pressure was maintained at 25 mm Hg. Drying wascontinued until final moisture content of the sample reached less than 2 % wet basis. Moisture lossduring drying was measured at 3 minute intervals. For every 3 minute drying interval, changes involume, bulk density, moisture content and compressive elastic modulus were measured for eachpower level. Drying kinetics was used to describe both macroscopic and microscopic mechanisms ofheat and mass transfer, which were affected by drying conditions, drying methods and type ofmaterial used for drying. Drying kinetic models are useful for equipment design, process optimizationand quality improvement of products. Experimental drying kinetic data were fitted to a mathematicalmodel developed based on the power absorbed by the material and time of drying at a givenpressure level. Also the experimental drying data points were fitted to an empirical model equation.Model constants were verified with another set of experimental data.