Effect of shear rate in high shear mixing process on the structure of cassava starch granule and reducing sugar product

Abstract

Cassava starch is one of the biopolymers which can be degraded to many useful products such as reducing sugar, non-reducing sugar and modified starch. However, it has a solid granule structure that can inhibit its degradation process. High shear mixing (HSM) is a well-known method for dissolving biopolymers. Shear effect of HSM created by a narrow slit between rotor and stator which can be increased by the increase of rotational speed. By increasing its shear effect, HSM is able to cut the glycosidic bond of starch to produce reducing sugar. Therefore, this study aims to study the effect of high shear rate to granule structure and reducing sugar product. The HSM process was carried out on the suspension of cassava starch with a concentration of 1/20 (g/mL) for 15 min at various stirring speeds (5000-15000 RPM). Products produced from the process are separated between solid and liquid for analysis. Solid products were analyzed using Scanning Electron Microscopy (SEM), Particle Size Analysis (PSA), and Viscometer Ubbelohde. While liquid products were analyzed using UV-Vis Spectrophotometry with the DNS method. Based on the experimental results, HSM produced reducing sugar up to 0.1972 mg/mL. Granule breakage was also observed by SEM and increasing of the nanoscale granule.