Processing high amylose wheat varieties with a capillary rheometer: Structure and thermomechanical properties of products

Eight types of novel wheat lines with different null alleles for starch synthase IIa, presenting different starch contents and amylose/amylopectin ratios, was processed on a lab-scale with capillary rheometer under 2 conditions (28% moisture content at 140 °C and 28% moisture content at 110 °C) in order to obtain different degrees of starch transformation. The thermomechanical properties measured by DMA were explained by the composite structure of the products, i.e. gluten dispersed in starch matrix, as observed by fluorescence microscopy. To explain the storage modulus variation with the flour composition, isostress-isostrain model was applied as a function of starch content. The discrepancies with this model are probably related to the variation of amylose/amylopectin ratio. This study finally pointed to the impact of the phase volume of starchy matrix and fillers on the material functionality.