Rheological properties of starch and kaolin mixtures in water during and after heating

Gelatinization characteristics of the starch and kaolin mixtures were investigated with the Brabender viscograph at starch concentration of 40 g/l and different kaolin concentrations from 0 to 60 g/l. The properties of starch gelatinization were affected by the addition of kaolin. Above a kaolin concentration of 12 g/l had, an additional viscosity peak was seen at 73 °C. Further increase of kaolin concentration up to 60g/l led to an increase is the additional peak at 73 °C, while the value of maximum viscosity peak decreased. eological features of gelatinized starch and kaolin mixtures were also investigated. Dependence of shear stress on shear rate was obtained with the use of Haake RS 100 rheometer with Z 38 AL sensor. Shear rate was first increased from zero to 200 s−1 and then decreased from 200 s−1 to zero within 400 s period. Those measurements were obtained at the 20, 40, 60 and 70 °C for the mixtures containing 10 or 20 g/l of starch and for kaolin concentrations ranging from 0 to 15 g/l. The results showed the independence between final viscosity and kaolin concentration in the mixtures. Viscosity was affected only by the temperature of the measurment and the starch concentration (10 or 20 g/l). ematical model for the rheological behavior of gelatinized starch, was developed which contains the number and volume of macromolecule aggregates as well as the number of bonds between aggregates. According to this model, the bonds energy between the aggregates reached the value of 2–8 kJ/mol, which seemed to be close to the Van der Waals bonds energy.