Influence of Processing Methods on Mechanical and Structural Characteristics of Vacuum Microwave Dried Biopolymer Foams

Control of physical and mechanical properties of biopolymer (derived from food hydrocolloid) porous solids in terms of stress strain relationship during compression, porosity and pore size would enable their use for a wider range of purposes. Different types of dried cellular biopolymer foams were produced using different food hydrocolloids such as locust bean and alginate gums, gelatin, low and high methoxy pectin, methyl cellulose and starches (corn and tapioca) at various proportions. First different types of wet hydrogels were prepared by varying gel processing methods. Then they dried using microwave energy under vacuum called vacuum microwave drying. Before performing the drying process the initial Young's modulus of the hydrogels was measured. Pore size analysis and distribution percentage were done using mercury pore size analyser after drying. Relationship between the pore size distribution after drying and the initial Young's modulus was developed. Compressive test was performed for dried porous solids and true stress strain relationship curves were developed to classify nature of dried foams obtained from various gel types. Scanning Electron Microscopic study of individual samples was performed to view the internal structure of dried porous biopolymers.