Effect of Extrusion Temperature and Moisture Content of Corn Flour on Crystallinity and Hardness of Rice Analogues

摘要

Rice analogues are food products made of broken rice and/or any other carbohydrate sources to have similar texture and shape as rice. They are usually made by hot extrusion processing. The hot extrusion process may change the crystallinity of starch and influence the characteristic of rice analogues. Therefore, this research aimed to study the effect of moisture content of incoming dough and temperature of extrusion process on the crystallinity and hardness of resulting rice analogues. The dough's were prepared by mixing of corn starch-flour with ratio 10/90 (w/w) and moisture content of 35%, 40% and 45% (w/w) and extrusion process were done at temperature of 70, 80, 90°C by using of twin screw extruder BEXDS-2256 Berto. The analyses were done to determine the type of crystal, degree of crystallinity, and hardness of the resulting rice analogues. Our result showed that the enhancement of extrusion temperature from 70 - 90°C increased degree of crystallinity from 5.86 - 15.00% to 10.70 - 18.87% and hardness from 1.71 - 4.36 kg to 2.05 - 5.70 kg. The raising of dough moisture content from 35 - 45% decreased degree of crystallinity from 15.00 - 18.87% to 5.86 - 10.70% and hardness from.4.36 - 5.70 kg to 1.71 - 2.05 kg. The increase of degree of crystallinity correlated positively with the increase of hardness of rice analogues (r= 0.746, p= 0.05).