Molecular features of wheat doughs enriched with perennial wheatgrass (Thinopyrum intermedium) flour

Thinopyrum intermedium - commonly known as intermediate wheatgrass (IWG) - is a perennial crop characterized by many desirable agronomic traits, such as high biomass yield, and drought and frost resistance. As a perennial, IWG has a longer growing season and much greater root mass than annuals, thus increasing carbon sequestration and reducing erosion risks and nitrate leaching. Therefore, it can positively impact on the environment, and it could successfully replace annual crops - as cereals are - for food production, especially on marginal agricultural lands. Moreover, the high fiber and protein contents (Bunzel et al., 2014), increases the interest in using IWG for human consumption. Consequently, more information about the starch and protein features of this crop is required. The aim of this study was to investigate the properties of starch and proteins in IWG-only and IWG/wheat systems. IWG based doughs were prepared at ≥50% IWG enrichment in order to produce systems with a total fiber content higher than 10%. The pasting properties of starch were evaluated. Proteins in the various dough samples were characterized in terms of extractability, total and accessible thiols; and structural properties, assessed by ATR-FTIR spectroscopy. Gluten aggregation properties (using GlutoPeak) and mixing profile (using Farinograph) were also considered. The predominant presence of starch granules in IWG assembled together could provide an explanation why the onset temperature of gelatinization phenomenon in IWG is 4°C higher than that in wheat. IWG proteins were able to aggregate and to generate torque. IWG-enrichment resulted in faster gluten aggregation and lower peak torque compared to hard wheat flour (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. From the standpoint of mixing, 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. In IWG-enriched doughs, beta-sheets represent the predominant structures as in the control dough. However, IWG-enrichment enhanced the non-sheet/sheet ratio, by increasing the unordered structures at the expenses of β-sheet structures but without affecting beta-turn structures. The overall results suggest that a 50% IWG-enrichment represents a good compromise between nutritional improvement and maintenance of the starch and protein characteristics in dough. Bunzel M, Tyl CE and Ismail B, Chemical composition of intermediate wheatgrass. in American Association of Cereal Chemists Annual Meeting. October 5-8, 2014. Provicence (RI) (2014).