Effect of sodium dodecyl sulphate on the physicochemical, thermal and pasting properties of cassava starch

The effect of different concentrations of sodium dodecyl sulphate (SDS) on cassava starch properties after complexation and in situ addition were studied. The swelling volume of the starch-SDS complexes increased to a maximum of 100 mL/g with increase in concentration of SDS (even at 0.004 mol SDS) with a corresponding decrease in solubility. During in situ addition also, a similar but gradual behaviour was observed for swelling volume and solubility. The apparent and total amylose contents showed an irregular trend. The soluble amylose content decreased with increase in concentration of SDS. In vitro enzyme digestibility of starch-SDS complexes was significantly lowered compared to that of native starch. The water-binding capacity showed an initial decrease followed by a significant increase at higher concentrations of SDS. DSC studies showed that in addition to the gelatinisation endotherm, a peak corresponding to the melting of the starch-SDS complex was obtained in the case of in situ addition of the surfactant. The peak viscosity of starch during in situ addition of SIDS exhibited a rapid increase except at the highest concentration. The peak viscosity of starch-SDS complexes underwent an initial reduction followed by a gradual increase at higher concentrations. The breakdown, setback and pasting temperature were also affected.