Effects of substitution level and particle size of extruded soybean hull fractions on physicochemical and sensorial properties of high-fiber pan bread during storage.

The effect of adding different fractions of extruded and non-extruded soybean hull to wheat flour at 20% and 30% and two-particle size levels (smaller and larger than 150 μm) was studied on the physicochemical, sensorial properties, and the shelf-life of high-fiber molded bread. Increasing the amount of all different fractions of the soybean hull raised the water absorption of the dough. It also increased the ash and crude fiber contents, bread crust lightness, redness and yellowness, bread crumb hardness as well as the cells number per unit area of the crumb. Moreover, it reduced the moisture content, specific volume, porosity, and overall acceptability of the pan bread. The treatments containing the fractions with larger particle sizes of the soybean hull had higher dough stability time, bread-specific volume, porosity, and lightness, as well as lower crumb hardness and moisture content, and crust redness and yellowness than the corresponding ones with finer particle sizes. The samples prepared with the extruded fractions with smaller particle sizes showed lower moisture content, hardness, porosity, and specific volume. After studying the bread staling, moisture content and overall acceptance of the samples decreased. In addition, the enthalpy in differential scanning calorimetry DSC) and the signal intensity in x-ray diffraction (XRD) increased during storage. In many cases, the bread with the large-sized extruded fractions of soybean hull at the substitution level of 20% was the most suitable product in most of the variables studied.