Effect of fatty acids on the rheological behaviour of amylomaize starch dispersions during heating

The pasting behaviour of 20% high-amylose maize starch dispersions in the presence of myristic, palmitic or stearic acid anions was monitored by on-line measuring parameters, such as torque development, pasting temperature, viscosity exhibited and granule swelling. The results indicated that the pasting process was affected by the fatty acid chain length with myristic acid to promote, whereas palmitic and stearic acids to suppress it. The flow behaviour of amylomaize starch dispersions heated at 75, 85 or 98 °C was examined at these temperatures, in the presence of the above mentioned fatty acids. It was found that the rheological characteristics of the samples heated at 75 °C were those of shear thickening fluids whereas for the samples heated at 85 °C or 98 °C were those of either Newtonian or pseudoplastic fluids. This behaviour was found to be dependent on the fatty acid chain length. To explain the above mentioned effects of fatty acid addition to amylomaize aqueous dispersions during pasting as well as during heating, certain mechanisms were proposed which involve possible granule–granule interactions and complexed with lipids amylose molecules – granule interactions.