Abstract
Rice is one of the most important staple foods in Asia, including Indonesia. Despite great efforts to increase rice production in Indonesia, imported rice is still needed due to high per capita consumption coupled with high population growth. One approach to overcoming these problems is to prepare extruded rice analogues by using yellow corn flour (maize flour or cornmeal) and corn starch as the base material. The dough moisture content and the extrusion temperature can influence the degree of gelatinization of rice analogues, which in turn affects the hardness of the rice analogue. This research studied the effects of dough moisture contents of 35%, 40%, and 45% and extrusion temperatures of 70°C, 80°C, and 90°C on the degree of gelatinization and the crystallinity of the resulting rice analogue. Raw materials used in this study were yellow corn flour, corn starch, glycerol monostearate and water. A twin screw extruder was utilized, operating at a screw speed of 75 rpm and a feed rate of 42.2 kg of dough per hour. The degree of gelatinization of the produced rice analogue was analyzed by differential scanning calorimetry (DSC) and polarized light microscopy, and the crystallinity was analyzed by X-ray diffraction (XRD). Our results showed that the dough moisture contents and extrusion temperatures examined in this study caused the starch granules gelatinized completely (degree of gelatinization 100%). The A-type crystals of corn flour and corn starch changed into V-type crystals after being extruded into rice analogues, which may be due to the formation of lipid-amylose complex compounds.
