ULTRASTRUCTURE OF SOY PROTEIN FIBERS FRACTURED BY VARIOUS TEXTURE MEASURING DEVICES

Spun soy fibers fractured by the tensile test, Warner-Bratzler shear, Kramer Shear Press and a modified Volodkevich wedge were examined with the scanning electron microscope. Fracture in the tensile test occurred almost always at a macrocavity, the weakest point in the fiber. Warner-Bratzler shear induced compression and flow at the zone of rupture, but not as markedly as in the case of the modified Volodkevich wedge. Fracture by the Kramer Shear Press was the closest to pure shear. Some of the exposed fracture surfaces revealed internal structures in the fibers such as macrocavities and distinct skin and core sections. The mechanism of rupture by these tests was more complex than expected.