Chemical Characterization, Functionality, and Baking Quality of Intermediate Wheatgrass (Thinopyrum intermedium)

Abstract

Environmental problems have exacerbated the challenges of food production. Soil erosion, run-off from irrigation, and greenhouse gas emissions have significantly impacted the ecosystem through their cumulative effects over decades. As the population increases, these aforementioned problems will grow in scale and scope. Thus, it is important to address these concerns by investigating sustainable solutions and conducting research on new approaches to food supply. Specifically, the development of perennial crops for food use would have environmental benefits such as reduced soil and water erosion. Further, the usage of perennial crops for food applications would provide alternatives to the current and ever diminishing food supply, provide incentives to farmers for planting these crops, and address consumers’ growing interest in sustainable food systems. One of several perennial crops available for potential food use is intermediate wheatgrass (IWG) (Thinopyrum intermedium). Little is known about the chemical and functional characteristics of IWG. Therefore, the overall objective of this work was to characterize the chemical and functional properties of IWG grains from multiple breeding lines for food applications, namely bread baking. Sixteen IWG experimental lines along with one bulk IWG sample and two wheat controls (Arapahoe and commercial hard red wheat) were analyzed for proximate composition following standard methodologies. Dietary fiber, total starch content, and percent damaged starch were determined using Megazyme kits. Amylose/amylopectin ratio and their molecular weight distribution were determined using size exclusion chromatography. Gluten forming proteins profile and molecular distribution were determined using gel electrophoresis and size exclusion chromatography. Dough rheology was assessed using a farinograph and a texture analyzer equipped with a Kieffer rig, while starch pasting properties were monitored using a rapid visco analyzer. Bread baking tests were performed following the AACCI 10-10.03 method. Compared to wheat controls, IWG samples had higher protein, dietary fiber, and ash contents, yet were lower in starch content and deficient in high molecular weight glutenins (HMWG), important protein components responsible for dough strength and elasticity. Specifically, wheat controls had more high molecular weight polymeric proteins (HMWPP), while IWG samples had more albumins and globulins. The ratios of amylose to amylopectin among the IWG samples and the wheat controls were similar. However, percent damaged starch was higher in the wheat controls than in IWG samples. On the other hand, the soluble to insoluble dietary fiber ratio was higher in wheat controls than in IWG samples. Dough rheology data showed that IWG dough was weaker than that of the controls. Farinograph and Kieffer data demonstrated that doughs made from wheat controls were more stable, more resistant to extension, and more extensible than doughs made from IWG samples. In terms of starch pasting properties, wheat controls had higher peak, hold, and final viscosities than the IWG samples, indicating the superiority of wheat controls over IWG samples as viscosity builders. The starch pasting properties data illustrated the samples’ behavior upon heating and cooling treatments, which are important characteristics to consider when evaluating IWG for commercial applications. Even though IWG had similar specific volumes to one of the wheat controls (hard red wheat), both wheat controls had a higher rising capability due to the wheat’s gluten network forming ability. Deficiency in HMWG and high fiber content of IWG samples, contributed to the poor gluten network and consequently inferior baking quality. Overall, results of this work suggest that IWG has a superior nutritional profile as compared to wheat, but poses challenges for baked products that require dough rising properties. Further studies on IWG, such as investigating the effect of conditioners on enhancing protein functionality, determining the effect of fiber on dough development, effect of blending with wheat, and exploring other food applications would enhance its potential utilization as a food crop. This research and future efforts will support breeders in their current screening and future breeding efforts for the development of IWG lines suitable for food applications.