Response Surface Method in Evaluating the Extrusion Effects on Molecular Degradation and Physical Properties of Sago Starch

Abstract

This study was aimed to measure the effect of extrusion on the molecular degradation and physical characteristics of the sago starch by employing response surface method. The starch was extruded in a twin screw extruder with moisture contents of 25, 32.5, and 40%; melt temperature of 86, 95 and 104oC; and screw speed of 100, 150, and 200 rpm. The extruded products were then analyzed for degree of molecular degradation, reducing sugars of the water soluble materials, water solubility index (WSI), water absorption index (WAI), enzyme susceptibility, gelatinization endothermic energy (∆H), and specific mechanical energy (SME). Increased mechanical and thermal energy input received by the products in the extruder gave rise to a significant degradation of the molecular weight of the macromolecules. It was believed that granule structures of the extruded starch have been reshaped. The extrusion process conditions did not significantly affect the WSI, WAI, reducing sugar content, and ∆H. All extruded samples had a much lower gelatinization endothermic energy than native starch.