Changes in physicochemical and structural properties of tapioca starch after high speed jet degradation

Tapioca starch (TS)suspensions (10%, w/v)were subjected to high speed jet (HSJ)processing at 80, 120, 160, 200 and 240 MPa for one pass, and the effects of HSJ treatment on solubility, rheological, pasting, morphological and molecular properties were further investigated. Polarized light microscopy observation revealed TS was partly gelatinized, and the number and clarity of“Maltese cross” decreased with the increase of HSJ pressure. The solubility of TS was increased significantly from 1.59% (0 MPa)to 12.11% (240 MPa). Dynamic oscillation analysis showed that TS gels displayed less elastic and more liquid like after HJS treatment, and all samples displayed pseudo-plastic properties during flow properties analysis. Rapid Visco Analyser measurement indicated that treated samples showed significantly decreased in peak viscosity and exhibited a lower tendency towards retrogradation on cooling process compared to untreated TS. Size-exclusion chromatography analysis suggested that the degradation of TS happened during HSJ treatment, and the degradation was more prominent beyond 160 MPa. The results showed that the significant changed in physicochemical and structural properties of treated TS were related to its degradation. These observations would provide an alternative and environmentally approach for starch modification.