Structural Characterization of Proteins in Wheat Doughs Enriched with Perennial Wheatgrass (Thinopyrum intermedium).

Intermediate wheatgrass (IWG) (Thinopyrum intermedium) 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. However,  characterization of the crop is necessary in view of the development of IWG-based products. The aim of this study was to investigate protein functionality in IWG and IWG/wheat dough. IWG-enriched doughs were prepared at high level of IWG flour (50, 75 and 100%) mixed with wheat flour in order to produce doughs with total fiber content higher than 10%, which is the threshold for significant nutritional benefits from IWG enrichment. Proteins in the various doughs were characterized in terms of solubility, thiols accessibility, and secondary structure as assessed by ATR-FTIR spectroscopy. IWG proteins did not develop into a viscoelastic network as wheat dough (used as a control) did. This behavior was attributed not only to the high fiber content but also to differences in protein profile and secondary structure. Protein characteristics of IWG dough exhibited a large amount of thiols and a network stabilized by non-covalent interactions. In IWG-enriched doughs, as in control dough, beta-sheet represented the predominant secondary structure. However, IWG-enrichment had higher non-sheet/sheet ratio, due to higher amount of unordered structures at the expenses of β-sheet structures. Results indicated that 50% IWG-enrichment represents a good compromise between nutritional improvement and maintenance of protein characteristics in dough. The impact of protein structural characteristics on extensibility and bread-making performances of IWG-enriched doughs needs further investigation.