Functionality of soymilk powder and its components in fresh soy bread.

The physicochemical changes upon addition of soymilk powder (SMP) to soy bread were investigated. Two-pound loaves of soy bread were produced with components (soluble fiber [SF], insoluble fiber [ISF], soy protein) that mimic those levels contributed by SMP. Soy flour and soy flour/SMP soy breads served as controls. The following were determined for all breads produced: physical properties (loaf volume, crust, and crumb color); chemical compositions (SF and ISF contents, protein and ash contents); and physicochemical properties (water activity, total moisture content by thermogravimetric analysis [TGA], "freezable" water [FW], "unfreezable" water [UFW] content by DSC, stiffness at 25 degrees C by dynamic mechanical analysis [DMA], and firmness with Instron testing machine). SMP contained significant amounts of SF aside from the ISF fraction and mostly denatured soy protein. SMP addition to soy bread formulation significantly decreased loaf volume with respect to control soy bread, which can be attributed to the ISF and SPI contents of this ingredient. Other effects of SMP were found to be lighter and yellowish crumb color, darker crust color, and increase in firmness, as well as no change in moisture content, FW and UFW contents, water activity, and stiffness parameters.