MECHANICAL-PROPERTIES OF EXTRUDED HIGH AMYLOSE STARCH FOR LOOSE-FILL PACKAGING MATERIAL

Extrudates of corn starch containing 700g/kg amylose, which may have p otential as a loose-fill packaging material, were prepared using an AP V Baker MPF50/25 twin-screw extruder Their moisture sorption isotherm was established by equilibrating them over saturated salt solutions at 25 degrees C. The salts used and their water activities (in parenthes es) were: LiCl (0.11), CH3COOK (0.23), MgCl2 (0.33), K2CO3 (0.42), Mg( NO3)(2) (0.53), NaNO2 (0.63), and NaCl (0.75). Energy index (3-19.3 N . m/m(3)), compressive strength (34-162 kPa), and spring index (58-79% ) of the packaging materials were determined from their stress-strain curve using the Instron Universal Testing Machine with a data acquisit ion system. Both energy index and compressive strength increased with increasing Water. activity levels up to 0.53 and then decreased. The s pring indices were not present rat water activities 0.11 and 0.23, and behaved in a similar manner to compressive strength at higher water a ctivities.