Quality assessment of bread prepared from blends of wheat flour and defatted soybean flour

Abstract:

Composite bread, defined broadly as bread in which wheat flour is partly substituted by flour from another cereal, legume or tuber, has been on the research agenda of cereal chemists for close to six decades. This research assessed the quality of bread prepared from five wheat : defatted soybean flour blends (100:0, 95:5, 90:10, 85:15 and 80:20) in terms of protein content, loaf volume, crumb texture, colour, and sensory acceptability. Bread was baked using the straight dough method at the Department of Agricultural Sciences, Lagos College of Food Technology, between August 2022 and February 2024. Protein content rose from 10.4% in the control to 19.8% at 20% soybean substitution. Loaf volume, however, dropped from 612 cm³/100 g at 0% substitution to 458 cm³/100 g at 20%. The 10% blend gave the best balance: protein at 14.3%, loaf volume at 574 cm³/100 g, and the highest overall acceptability score (8.4 on a 9-point scale). At 20% substitution, crumb firmness rose sharply (9.6 N against 3.8 N in control), pointing to gluten dilution as the main quality limiter. Textural properties were validated on a TA-XT2 analyser. Findings indicate that 10% defatted soybean flour substitution meaningfully raises the protein density of bread without unacceptable compromise on volume, texture or sensory quality, offering a practical route to protein enrichment of everyday bread.