Rheological characteristics of binary composite gels of wheat flour and high amylose corn starch.

The effect of addition of high amylose corn starch (Hylon VII or H) to wheat flour (WF) on the mechanical properties of the resulting binary composite gels (BCG) under small and large deformations was evaluated. To this end, the composite gels at different ratios of WF/H including 95:5, 90:10, and 85:15 were tested under a linear viscoelastic regime (LVE) in oscillatory angular frequency and a texture profile analysis in compression mode. However, the gel firmness was increased by Hylon VII addition, but the springiness was reduced. Since the adhesiveness and cohesiveness were not significantly different, no dilution effect was observed for the samples. Furthermore, the dominance of G' than G″ over the range of LVE and high fracture stress at high level of Hylon VII confirmed the high gel strength which can be attributed to the retrogradation of amylose and reduction of amylopectin from WF. The less frequency dependency of BCG revealed the solid-like response and strong gels structures with more elastic network. High value of α revealed a lower number of interactions within the gel network structures. Consequently, due to the high gel strength of BCG of WF/H, it can be exploited at high thermal operations such as retort processing as well as it can be utilized for dysphagia therapy due to the special textural parameters.

PRACTICAL APPLICATIONS: Small and large deformation properties can provide profound insights toward the gel structure. The former gets knowledge about dynamic rheology and the latter gives the textural properties of the gel matrices. Since, achieving the desired texture of foods has a chief impact on the target consumers, and chewing and swallowing disorders such as dysphagia are common problems in older people, more effort is needed to modify the texture of food with a soft structure. On the contrary, supplying a more gel strength network, which can withstand at high thermal processing and not collapse, is so vital. Therefore, the current work was accomplished to provide some knowledge about the binary composite gel of WF and Hylon VII starch such as the gel strength, fracture stress, fracture strain and material stiffness which enables us to evaluate the nature of starch gels for further applications such as drug delivery systems, elderly diet and further processes.