Influence of different pretreatments on the quality of wheat bran-germ powder, reconstituted whole wheat flour and Chinese steamed bread

Abstract

This paper studied the influences of low-temperature (temp) extrusion (nonexpanded), high-temp extrusion (expansion), explosion puffing and high-temp jet milling on the modification of wheat bran-germ powder (WBGP) and on the dough properties, storage stability and Chinese steamed bread (CSB) quality in relation to reconstituted whole wheat flour (WWF). The four pretreatments significantly increased the soluble dietary fiber content of WBGP by 79.0%, 72.8%, 47.6% and 70.9%, respectively, and the lipase and lipoxygenase activities were inactivated to varying degrees. The extrusion technologies did not cause significant changes in the gluten indexes and pasting properties of WWF, while the low-temp extrusion had better thermal stability and anti-retrogradation. The gas retention coefficients of WWFs were pretreated by extrusion was higher than the other WWFs. The specific volume of CSB pretreated by low-temp extrusion was slightly larger than that of control, and the cell diameters and coarse cell volumes were smaller. Pretreatment can obviously inhibit the increase in fatty acid contents of WWF during storage and inhibit enzyme activity. The storage stability of extrusion technologies was better than that of wheat flour. Altogether, low-temp extrusion was more suitable for pretreating WBGP.