This study focuses on evaluating the physico-chemical properties of extruded cassava starch added with corn flour. The raw materials were mixed at different ratios (corn flour/cassava starch 0:100, 25:75, 50:50, 75:25, 100:0 [w/w]), then extruded at different barrel temperatures (120 and 140°C) and moisture contents (20 and 25%), with the physicochemical and pasting properties of extrudates finally analyzed. The obtained results showed that the addition of corn flour to the mix resulted in an increase in specific length, lightness, yellowness, water absorption index, water solubility index, final viscosity, and setback viscosity of extrudates, while there was a decrease in redness and piece density. Other properties including the expansion ratio, reducing sugars, cold viscosity, peak viscosity, hold viscosity, and breakdown viscosity were more likely to be subjected to barrel temperature and moisture content. Mixing corn flour with cassava starch ameliorated the expansion properties, color, and some pasting properties of mixed extrudates. This study demonstrated that the use of corn flour and extrusion process with different barrel temperatures and moisture contents provided valuable data for the further development of extruded cassava starch.
Higher level of KCl application stimulated both leaf area index and leaf area duration in all cassava varieties, while the leaf and tuber number of the bitter varieties (high cyanide-level varieties) decreased in proportion to the level of KCl application. The root/shoot (R/S) ratio and harvest index (HI) were negatively related with the level of KCl application in all cassava varieties. The bitter varieties obtained the lowest R/S ratio at the level of 100 - 150 kg KCl ha-1 , while the sweet varieties (low cyanide-level varieties) acquired the highest values at the level of 50 - 150 kg KCl ha-1 . Also, the sweet varieties showed the lowest HI at the level of 250 kg KCl ha-1 , but the bitter varieties at the level of 150 kg KCl ha-1 . At 6 - 8 months after planting, the sweet varieties tended to obtain higher starch content of roots (tubers) at the level of 50 - 150 kg KCl ha-1 , while the bitter varieties at the level of 150 - 250 kg KCl ha-1 . Relatively lower level of 50 - 150 kg KCl ha-1 was more appropriate for decreasing hydrocyanic acid (HCN) content of roots (tubers) in the sweet varieties at the harvest time, and the level of 250 kg KCl ha-1 was adequate to decrease not only HCN content of leaves but also that of roots (tubers) in the bitter varieties during the growing period. To obtain higher yield and starch content of tubers, and lower HCN content of roots (tubers), it was recommended that the sweet varieties are applied with the level of 50 - 100 kg KCl ha-1 and the bitter varieties with the level of 150 - 200 kg KCl ha-1 , respectively, in Latosol soils of Bogor areas, West Java.