Rate Modelling of Alkali Gelatinization at Low Conversions

The rate of starch gelatinisation under strong alkali conditions was modeled at low conversion (x < 0.4), with the degree of gelatinisation (conversion) defined in terms of sample viscosity. Experimental data at low conversion were fit to eleven rate models based on the mechanism of the unreacted-core model and the rate controlling steps determined. Film diffusion (stokes regime) plus Product layer diffusion steps control the rate of reaction for all sodium hydroxide concentrations and at low conversion (x < 0.4), with the dominance shifting from Film diffusion to Product layer diffusion as sodium hydroxide concentration is increased.