Cereal Chem 68:413-418   |  VIEW ARTICLE

Effect of the Hard-to-Cook Defect and Processing on Protein and Starch Digestibility of Cowpeas.

Y.-H. Tuan and R. D. Phillips. Copyright 1991 by the American Association of Cereal Chemists, Inc. 

Cowpeas were stored for six weeks at 37 C and 85% rh for a test group and at 7 C and 60% rh for a control group. After storage, they were treated as follows: cooked for 45 min; cooked for 90 min; ground into a flour; made into a flour slurry (20% solid) and cooked as a gruel for 45 min; or ground into flour and extruded at 20% moisture with a barrel temperature of 150 C. The hard-to-cook defect was observed in the test group. The effect of storage conditions and processing treatments on the nutritional quality of cowpea protein and starch was determined by in vitro and in vivo (fecal and ileal digestibility) methods. The in vitro and ileal methods indicated that the protein digestibility of the control group was significantly higher than that of the test (hard-to-cook) group (78.5 vs. 75.3% and 76.9 vs. 66.6%, respectively); the fecal assay detected no difference. In vitro and ileal protein digestibility was highest in cowpeas cooked for 45 min (80.3 and 81.8%, respectively) and lowest in cowpeas ground into flour (72.6 and 65.4%, respectively). Grinding before processing exacerbated the differences between the control and the test groups. Starch digestibility was enhanced by grinding before cooking but showed little response to storage conditions.