Adding soy flour to bread at different levels affects its characteristics. The study tested levels from 2-12% and found changes in dough properties, color, texture, and protein content. Soy flour increased water absorption, weakened dough, and decreased developing time. Bread with soy flour was darker, coarser, and had higher protein content. Volume decreased with 4% soy flour, but adding 0.5% sodium stearoyl-2-lactylate helped. However, at 10-12% soy flour, volume reduction was not prevented. Overall, soy flour improved protein concentration and quality of bread.