and developed a power-law correlation
between the mechanical properties and bulk density of the foams made from maize grits. Chinnaswamy and Hanna [11]
reported that the optimum temperature for maximum expansion of cornstarch extrudates increased from 130°C to 160°C, as
the amylose content increased from 0 to 70%, and the bulk density of the extrudates decreased as the amylose content in the
starch increased. Our results indicate that minimum density of high amylose starch foams was obtained at temperatures of
105°C to 110°C, with an increase in density at higher and lower temperatures. Warburton et al. showed that the Young’s
modulus [12] and fracture stress [13] decreases with increasing starch content. Bhatnagar and Hanna [14] extruded regular
cornstarch with either polystyrene or poly (methyl methacrylate) at a 70:30 ratio with other additives in a single screw
extruder. Foam densities in the range of 29.5-132 kg/m3 were obtained, with radial expansions of 8.8 - 40.1. Wang et al.
[15] showed that cornstarch foams had better radial expansions but higher unit and bulk densities as compared to wheat
starch foams.
Cha et al. [16] studied the moisture adsorption isotherms, bulk densities and expansion ratios of the starch-based
foams involving about 33% synthetic polymers (polystyrene), which reduces its biodegradability. They showed that the
bulk density of the starch foams decreased with an increase in extrusion temperature up to 160°C, but highest expansion
was obtained at 140°C. Also, chemical blowing agents were used in addition to water as the physical blowing agent.