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ABSTRACT

High protein fractions (HPF) of navy and pinto beans were mixed with high starch fraction (HSF) or corn meal and extrusion-cooked. HSF of pintos blended with hull fractions was extruded at 132°C. Expansion index (EI), density, color, water absorption (WAI), water (WSI) and nitrogen solubility (NSI), oil absorption (OAC) and emulsification (OEC) were evaluated. Extruded blends had lower EI and OAC, higher protein density and OEC than extruded corn or HSF. WAI and WSI were variable. EI decreased with increased protein. Scanning electronic microscopy showed protein level had pronounced influence on microstructure, size of air cells and smoothness of cell walls. Hull fraction added to HSF, caused decreases in EI, WAI, WSI while NSI, OAC and OEC were unaffected.