Rheological properties of perennial wheatgrass (Thinopyrum intermedium) and its blends with wheat flour

Intermediate wheatgrass (IWG) (Thinopyrum intermedium) is a perennial grass with desirable agronomic traits and positive effects on the environment. Its high fiber and protein contents have increased the interest in IWG for human consumption. As for improvement of IWG potential for food production, efforts are tied to understanding the functional properties of IWG. The aim of this study was to investigate starch physical properties and protein aggregation in IWG-only and IWG/hard wheat (HWF) systems. IWG-based doughs were prepared at 50%, 75% and 100% IWG levels in order to produce systems with total fiber content higher than 10%. The pasting properties of samples were evaluated using Micro Visco-Amylograph. Proteins in the various blends were characterized in terms of extractability, readily and SDS-accessible thiols. Gluten aggregation properties (using GlutoPeak) and mixing profile (using Farinograph) were also considered. IWG-enrichment increased the pasting temperature and decreased peak viscosity of blended flours. The former is related to the predominant presence of starch granules in IWG assembled together, whereas the latter to fiber content. IWG proteins were able to aggregate and form a gluten-like network that was less strong than HWF (GlutoPeak test). IWG-enrichment resulted in faster gluten aggregation and lower peak torque compared to HWF, suggesting a weakening of the gluten network. This is related to the high protein solubility of IWG. Moreover, despite the high level of thiol groups, these seem not to be as available for aggregating as in HWF. During mixing, IWG-enrichment resulted in an increase in consistency and a decrease in development time and dough stability, likely due to the higher levels of fiber and to differences in protein profile. The overall results suggest that 50% IWG-enrichment represents a good compromise between nutritional improvement and maintenance of the pasting properties, protein characteristics and gluten aggregation kinetics.