Effects of Dough Conditioners on Rheology and Bread Quality of Intermediate Wheatgrass

Abstract

Studies have shown the detrimental effect of agricultural practices on the environment. One solution to combat those problems would be to focus on alternatives that would lead to sustainable environmental benefits, like cultivating perennial crops. While annual crops are dominating current agricultural production, cultivating perennial crops would contribute to several environmental benefits like reduced nitrogen losses, and soil erosion. With expanding global food insecurity, using perennial crops for food would offer an alternate to diminishing food supply. Among the several perennial crops screened for domestication, intermediate wheatgrass (Thinopyrum intermedium, IWG) has been considered a promising crop to be used as food. The aim of this study was to evaluate IWG of same genetic material, cultivated at two location in Minnesota- Rosemount (RM) and Roseau (RS) for chemical and functional characteristics of dough and breads as affected by refinement (bran removal) and the use of dough conditioners. Five dough conditioners were used- wheat protein isolate, (WPI), vital wheat gluten (VWG), ascorbic acid (AA), Powerbake (a commercial enzyme mix) (PB) and transglutaminase (TG). While IWG kernels were studied for kernel physical properties, IWG flour at three refinement levels - 0 %bran (0B), 50 %bran (50B) and 100 %bran was investigated for proximate composition and dietary fiber following respective standard methods. Dough extensibility and resistance to extension were measured with the texture analyzer equipped with Kieffer extensibility rig, and dough stickiness was measured with a texture analyzer equipped with Chen-Hoseney stickiness cell. Baked breads were evaluated for dimensions, specific volume, crumb firmness, and crumb grain characteristics. Controls consisted of annual hard red winter wheat (W) and IWG dough without conditioners (N). IWG kernels were thinner, with lower weight, volume and bulk density in comparison to wheat. Results from proximate composition indicated an increased fat, protein and ash content with increasing bran concentration, and a decrease in moisture and carbohydratecontents. While there was no difference between IWG and wheat at 0B for moisture and carbohydrate, for the remaining two bran concentrations, wheat had higher moisture and carbohydrate, and lower protein, fat and ash content than IWG. IWG had higher dietary fiber content than wheat at 50 and 100B refinement levels, the difference attributed to insoluble dietary fiber, as no differences was observed in soluble fiber between wheat and IWG at all bran concentrations. At all bran concentrations, extensibility of wheat dough was higher than for the dough made with IWG from both locations. Adding dough conditioners did not improve extensibility for any samples. Some differences were noted between the two locations- 50B-N, 50B and 100B with WPI, 100B with VWG, 50B and 100B with AA, 50B and 100B with PB and 0B and 100B with TG. At 0B and 50B, resistance to extension of wheat dough was higher than for dough made with IWG from both locations, however, for 100B, IWG from RM N, with AA, and PB and IWG from RS N, with WPI, VWG, AA and PB were different. TG increased resistance to extension for IWG from RM at 0B and 50B; for IWG from RS at all refinement levels. At all bran concentrations, stickiness of wheat dough was lower than for dough made with IWG from both locations. Adding PB and TG to 100B IWG from RM reduced stickiness to match values of wheat, however, no such effect was seen in IWG from RS. Adding WPI and VWG reduced stickiness of 0B IWG samples from both locations, in addition, TG also reduced stickiness of 0B RM IWG dough. While no conditioners reduced stickiness of 50B IWG from RS; WPI, VWG, PB and TG reduced stickiness of 50B IWG from RM. While dough conditioners did not reduce stickiness of 100B samples from RM; WPI, VWG and TG reduced stickiness of 100B samples from RS. Bread results indicated a negative effect of bran on dimensions, specific volume and crumb grain characteristics. While WPI, VWG, AA and PB improved or did not change the bread dimensions, TG always reduced them. The effect of dough conditioners was more pronounced for length and width than for height; indicating IWG expanded more than rose. While none of the conditioners increased the specific volume of RS IWG samples at any refinement level, PB increased the volume of 0B IWG from RM. TG decreased the specific volume of all samples. At 0B concentration, controls and breads with WPI and VWG demonstrated collapse when in oven. A noticeable surface smoothing effect was observed for 0B samples with AA and PB. AA and PB improved the crumb grain properties with uniform air cells distribution for 0B samples. Bran negatively affected the air cells count, and adding dough conditioners did not improve the crumb grain characteristics. While there was no effect of TG on 0B samples; cell count, cell area and cell size decreased with TG addition for higher bran contents. The breads were unacceptably dense and the effect was pronounced at higher bran concentrations. This work provides insight on ways to improve functionality and product quality of IWG breads. AA and PB produced loaf of consistent appearance with smoother surface and uniformly distributed gas cells in the crumb. WPI and VWG exhibited expansion before the dough collapsed and thus, the loafs were unable to hold gas. Adding starch or other functional ingredients to increase viscosity would help in retaining the gas, and is thus recommended. This research would facilitate future efforts towards using IWG as a standalone flour for breads, as well as help breeders for markers selections towards developing IWG bread flour.