Effect of bran reduction on gluten secondary structure in intermediate Wheatgrass (Thinopyrum Intermedium) Dough

Introduction: Thinopyrum intermedium, commonly known as intermediate wheatgrass (IWG), is a perennial crop with favorable agronomic characteristics; reduces soil and water erosion, increases nitrogen fixation and disease resistance. We have previously shown that in comparison to wheat controls, IWG lines had higher protein and dietary fiber contents. However, the protein distribution is significantly different from that of hard red winter wheat (HRWW). The difference in protein distribution coupled with higher fiber content negatively affects the dough rheology in terms of protein network formation. Therefore, the objective of this study was to determine the effect of bran reduction on the gluten secondary structure in IWG dough using Fourier transform infrared (FTIR) spectroscopy. Method: IWG grains sample was milled and bran was separated. Bran was added back to refined IWG flour at 100%, 75%, 50%, 25%, and 0% of original bran content. Using Differential Scanning Calorimetry (DSC), gluten protein glass transition temperatures at various moisture contents were determined to identify optimum dough forming conditions. Different flour samples were evaluated for dough strength using farinograph following the constant flour weight procedure according to AACC method 54-21.02. Dough samples were collected at different time points during mixing: dough development time, stability departure, and overmixing. Flour and dough samples were subjected to FTIR spectroscopy to determine changes in protein secondary structure. Significance: Determining differences in gluten secondary structure as affected by bran content during dough formation provides insights to gluten network formation and stability during dough mixing and baking. This information leads to optimization of IWG grain processing and utilization in order to expand its market potential. Results: The milling of IWG grains yielded 59% for bran and 41% for refined flour, while milling of wheat control yielded 40% and 60% respectively. The glass transition temperature of extracted gluten from IWG was 37°C compared to room temperature for gluten from control wheat at 16% moisture. Farinograph was carried out both at 30°C and 40°C for all the flour samples. Differences in secondary structure profile were noted between IWG and control wheat dough at the various mixing times.