Utilization of Corn Hominy as a New Source Material for Thermoplastic Starch Production

Corn hominy or ampok (in local language) is a by-product from corn milling industry. It is about 35% in weight of dry milled kernel. Corn hominy contains a small amount of fibre (7.26%), protein (10.2%), fat (8.12%), and a large amount of starch (63.21%) which could be used as an alternative source for making starch based thermoplastics (STP), hence reducing the use of starch. The aim of this research is to investigate the effects of weight ratio of tapioca to corn hominy as well as the glycerol content in formula compositions on mechanical properties, i.e. tensile strength and elongation at break and thermal properties (Tg and Tm) of corn hominy based thermoplastic. The ratio of tapioca to corn hominy composition varied from 0:100; 25:75; 50:50; 75:25 and the glycerol content varied from 25% to 35 wt%. The blends were melt processed using counter rotating twin screw mixer with the barrel temperature of 120, 130 and 120 °C at 60 rpm for 5 min. It has been observed that using corn hominy as a sole material for making thermoplastic was not feasible. The tensile strength, elongation at break, and glass transition point (Tg) were greatly affected by increasing the tapioca content. Thermoplastics starch produced by extruder was then pressed by a hydraullic press, and this showed good characteristics which signaled by homogenous surface of SEM images. The surface morphology of thermoplastic starch was unchange by increasing the glycerol content and corn hominy ratio. However, higher corn hominy ratio gave smoother surface morphology at the cross section of thermoplastic starch.