Insoluble starch composite foams produced through microwave expansion.

An insoluble biocomposite composed of potato starch and chitosan was prepared by microwave treatment. The effect of pH on swelling (liquid absorption) behavior of the composites was investigated at pH 2, pH 6.8 and pH 12. Analysis revealed that the solution uptake ratio of composites depends both on the aqueous pH value and the content of the chitosan. Composites exhibited a relatively high swelling ratio at pH environments lower than the pK(a) of amine groups on chitosan (about 6.3). Glucose analysis by ion exchange chromatography showed that there was little hydrolysis of such composites at low pH. When immersed in the same pH solution, composites with higher chitosan content exhibited higher swelling ratios. The microstructure of composites produced was also investigated by FE-SEM.