Changes in structural conformation of proteins in wheat flour doughs enriched with intermediate wheatgrass (Thinopyrum intermedium) flour

Intermediate wheatgrass (IWG) is a perennial crop whose development as an environmentally sound alternative crop for marginal lands has received recent attention among agronomists, plant breeders and environmentalists. The compositional attributes of IWG - high protein and fiber content - make this crop nutritionally attractive as well. The aim of the study was to explore the relationship between rheological properties and protein functionality in IWG-enriched dough. IWG was blended with hard wheat flour (WF; 15% protein) at IWG:WF ratios of 0:100, 50:50, 75:25 and 100:0. Dough samples were prepared in a Farinograph at a constant water absorption level (70%) that was optimal for WF. Dough samples were collected at peak development (6 and 2 min for WF and IWG-enriched doughs, respectively) and at two points during break down (14 and 20 min). Protein secondary structure was measured using ATR-FTIR spectroscopy. IWG-enrichment resulted in an increase in consistency and a decrease in dough development time and dough stability, likely due to the higher levels of fiber. Proteins in WF doughs had a large fraction of β-sheets (~45%) and β-turns (~35%) with a lower content of α-helical (~10%) and unordered structures (~10%). IWG enrichment resulted in a decrease in β-sheets with an increase in unordered structures at peak development time. Overmixing of WF and 50% or 75% IWG doughs resulted in a slight increase in β-sheets at the expense of β-turns, whereas α-helical and unordered structures remained relatively constant for the entire duration of mixing. In the case of 100% IWG, overmixing resulted in a decrease in β-turns and an increase in unordered structures, in line with the dough weakening shown by the Farinograph curve. Investigating protein interactions of IWG dough will increase the potential to create novel healthy products that are also environmentally sustainable.