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Some wheat cultivars show a linear relationship between grain protein concentration (GPC) and baking volume, but others display a saturation curve. Such a saturation curve could be general, but in some cultivars it might only appear at GPC > 17%. However, such GPC is mostly not achieved in the field. Pot experiments with high nitrogen application reliably result in GPC > 17%. In a pot experiment with a high (N1) and an excessive N level (N2) and four cultivars (Akteur, Arnold, Discus and Hystar), the change in grain protein composition and the relationship between different protein fractions and baking volume at GPC > 17% was investigated. GPC ranged from 17 to 24% and mean nitrogen content per grain from 1.2 to 1.8 mg. The N2 treatment increased GPC and mean nitrogen content per grain in the Akteur and Discus cultivar, but not in Arnold and Hystar. N2 increased concentration of gliadin by 10 to 34% and glutenin macropolymer (GMP) in all cultivars by 12 to 73%. Glutenin concentration was increased by N2 in Akteur and Discus (19 to 36%), but was decreased by N2 in the Arnold and Hystar cultivar. Baking volume was moderately increased by N2 in all cultivars by 6 to 9% and correlated significantly with most glutenin fractions in the Akteur and Discus cultivar, with GMP in Arnold and with HMW-GS to LMW-GS ratio in Hystar. Thus, specific effects on grain protein by N2 were responsible for the increased baking volume in each cultivar. However, as gliadin and its sub-fractions hardly correlated with baking volume, a positive effect of increasing gliadin proteins on baking quality was not obvious.

The fate of β-glucan (BG) health promoting properties during food production is crucial, but not predictable yet. Therefore, high molar mass BG (hBG) and control BG (cBG) were extracted from two barley varieties, characterized and added to wheat breads at levels of 3% and 6%. Bread quality criteria, carbohydrate contents and BG content and structural properties were determined. Additionally, breads were subjected to an in vitro digestion. The BG content in the chyme, molar mass, molar ratio, viscosity and bile acid retention were determined. The hBG and the cBG decreased loaf volume and increased crumb hardness with increasing BG content. The reduction in BG content during bread making was similar for hBG and cBG, but the molar mass of cBG decreased to a greater extent. As a result, only 10% of cBG entering in vitro digestion were found in the chyme afterwards, while 40% of the ingested hBG were detected. Molar mass reduction was much more severe for cBG compared to hBG. The use of hBG showed higher viscosity and better bile acid retention, indicating cholesterol lowering properties, compared to similar or higher amounts of cBG. These results provide valuable knowledge on the criteria to select BG-rich raw materials for ideal health promoting properties.

Amaranth and finger millet are important food security crops in Africa but show poor bread making ability, even in composite wheat breads. Malting and steaming are promising approaches to improve composite bread quality, which have not been fully explored yet. Therefore, in this study, wheat was blended with native, steamed or malted finger millet or amaranth in the ratio of 70:30. Wheat/native amaranth (WHE-NAM) and wheat/malted amaranth (WHE-MAM) had longer dough development times and higher dough stabilities, water absorption capacities and farinograph quality numbers than wheat/steamed amaranth (WHE-SAM), wheat/native finger millet (WHE-NFM), wheat/steamed finger millet (WHE-SFM) or wheat/malted finger millet (WHE-MFM). The WHE-NAM and WHE-MAM breads had lower crumb firmness and chewiness, higher resilience and cohesiveness and lighter colours than WHE-NFM, WHE-SFM and WHE-MFM. Starch and protein digestibility of composite breads were not different (p > 0.05) from each other and ranged between 95–98% and 83–91%, respectively. Composite breads had higher ash (1.9–2.5 g/100 g), dietary fibre (5.7–7.1 g/100 g), phenolic acid (60–122 mg/100 g) and phytate contents (551–669 mg/100 g) than wheat bread (ash 1.6 g/100 g; dietary fibre 4.5 g/100 g; phenolic acids 59 mg/100 g; phytate 170 mg/100 g). The WHE-NAM and WHE-MAM breads possessed the best crumb texture and nutritional profile among the composite breads.