A mechanistic model of the relation between molecular structure of amylopectin and macromolecular degradation during heating-shearing processes

A molecular scale model describing the molecular breakdown of low moisture amylopectin melts by shear forces was derived and compared to engineering scale experiments. The model is based on the assumption that the maximum shear stress on the polymer equals the effective surface stress on that polymer, which is related to the strength of the glycosidic bonds. The molecules are approximated as spheres, with a radius that exhibits fractal scaling with molecular weight. The molecular weight reduction as a function of applied shear stress as deduced from the model agrees satisfactorily with the results from experimentally obtained engineering scale data. The results show a successful example of a coupling between engineering scale experiments and micro-scale models and contribute to the understanding of fundamental changes in the properties of starch during industrial scale heating-shearing processes. (C) 2004 Elsevier Ltd. All rights reserved.