Effect of drying temperature on physicochemical properties of cassava starch

Physicochemical and pasting properties of cassava (Manihot esculenta Crantz) starch dried in open air and at different temperatures in a tray dryer were determined and the effect of drying temperature on these properties was investigated. The open air dried starch had a moisture content of 12.5%, ash - 0.76%, protein - 0.85% and fat - 0.16%. With amylose content of 23.45%, pH of 5.88 and average granule size of 14.1 mu m, the starch exhibited the A-type crystalline diffraction pattern which was not affected by drying temperature in the range of 40-60 degrees C when the starch was dried in a tray dryer. Starch degree of crystallinity decreased as the drying temperature increased in the above range. Water binding capacity and paste clarity increased, while swelling power and solubility, peak viscosity, breakdown viscosity, setback viscosity and peak time decreased significantly with increase in drying temperature (p<0.05). Freeze-thaw stability and pasting temperature decreased, while final viscosity increased significantly with increase in drying temperature, up to a point, and the trend reversed as the drying temperature increased further. Regression models that could be used to adequately express the relationships existing between the physicochemical and pasting properties of the starch and drying temperature were established.