Physical and nutritional impact of fortification of corn starch-based extruded snacks with common bean (Phaseolus vulgaris L.) flour: Effects of bean addition and extrusion cooking

Navy and red bean flours (BF) were added to corn starch at levels of 15%, 30%, and 45% and submitted to extrusion cooking to produce fortified puffed snacks. Process variables (screw speed, moisture. and temperature of the final zones) of a twin screw extruder were kept constant (150 rmp, 22% and 160 degrees C). Corn starch-bean extrudates were denser, less expanded, and harder. However starch fortified with 30% BF produced extrudates with percentage of deformation - all instrumental measurement of crispness-comparable to corn starch alone. At this level, crude protein was increased 12-fold, while total phenols, 2,2-diphenyl-1-picrylhydrazyl radical (DPPH center dot) and oxygen radical absorbance capacity (ORAC) in vitro antioxidant activities (AA) were also increased. Red bean fortification yielded extrudates with higher levels of phenols and both DPPH center dot and ORAC AA compared to navy beans. In navy and red bean extrudates, total phenols, DPPH center dot, and ORAC AA were reduced by 10%, 17%, and 10%, and by 70%, 62%, and 17% after extrusion, respectively. Phytic acid and trypsin inhibitors levels were reduced in nearly 50% and 100% in all bean extrudates compared to raw mixtures, indicating that these materials were safe for human consumption. (C) 2008 Elsevier Ltd. All rights reserved.