Rheology of wheat starch–milk–sugar systems: effect of starch concentration, sugar type and concentration, and milk fat content

Abstract

Studies have been undertaken to investigate the effect of sugars on the rheological properties of wheat starch–milk pastes. The wheat starch–milk–sugar (WMS) pastes were heated at 95 °C. The influence of sugar type and concentration, and milk fat content was deduced from the differences in the apparent viscosities and Herschel–Bulkley model parameters between these pastes. The WMS paste exhibited a typical shear-thinning behaviour. This behaviour was observed throughout the range of starch concentration and shear rates studied and could be attributed to stress-induced breakdown of the network structure. Sugars were found to increase the viscosity of wheat starch–milk paste in the order: glucose < sucrose < fructose. This order of the sugar effectiveness was independent of both the starch and sugar concentration, but it became more clear with increasing the starch concentration. Replacement of skim milk by water did not change the effectiveness order of sugars on the viscosity of the starch paste. On the other hand, the wheat starch–milk paste showed higher viscosity than wheat starch–water paste. The effect of milk on the viscosity of starch paste became more pronounced with increasing the fat content of the milk.