Environmental friendly polysaccharide modification – rheological properties of oxidized starches water systems



Detailed rheological studies were performed in order to characterize a new class of modified starches. The polysaccharide was oxidized in a paste using H2O2 coupled with sodium tungstate as a catalyst. Oxidation processes were carried out in microwave (µν) and conventional (Δ) conditions. Commercially oxidized starch (E1404) was used as a reference material. Further analysis covers the investigation on polysaccharides chains degradation as a key factor for rheological properties. Pasting properties of the new starches may have approximately 100 times lower viscosity. The viscosity of the paste does not depend on the heating method during the modification process (µν or Δ). According to that, it might be stated that pasting before modification is fundamental for the deep changes of rheological and osmotic properties detected for water solutions of oxidation products. The viscosity which increases with shear rate allows identifying all pastes as shear-thickening systems. Additionally, microscopic analysis was performed (AFM) in order to link the mechanical properties and inner structure of pastes obtained from modified starches. Results obtained allow to conclude that the investigated protocols (oxidation in paste) guide to the new class of oxidized starches. The oxidation follows the strong degradation of the starch, which affects in mechanical properties. The obtained material cannot serve as a thickening agent in food technology, although its properties may lead to other application possibilities like ion exchange or chelating agent.