Effects of extruder die temperature on the physical properties of extruded fish pellets containing taro and broken rice starch

A study was conducted to investigate the effects of starch source (taro and broken rice) and extrusion die temperature (125, 140, 155 and 170 °C) on the physical properties of extruded pellets. The blends containing taro or broken rice starch were extruded using a single screw extruder and the three zones of the barrel temperature profile were set constant at 70, 90 and 100 °C. Moisture content, expansion ratio, bulk density, floatability, pellet durability index, water absorption and solubility indices were extensively analysed. The results elucidated significant effects on the physical properties of the extruded pellets during the increase of die temperature and also change of starch source from taro to broken rice. The highest ER, PDI, WAI was noted in the fish diet containing broken rice starch compared to diet containing taro starch. Increase of die temperature from 125 to 170 °C has significant effects on physical properties of the extruded pellets containing taro and broken rice starch. The MC, ER, F, PDI and WAI values significant increased by 7.0, 3.5, 103.6, 0.1 and 13.5%, respectively, as the die temperature was increased from 125 to 170 °C. In contrast, there was a significant decrease in BD and WSI values by 9.4 and 12.2%, respectively, as the die temperature elevated from 125 to 170 °C.