Description

A poster presented at the 2012 Global Pulse Researchers Meeting, Kigali, Rwanda- “Transforming Grain-Legume Systems to Enhance Nutrition and Livelihoods”. Abstract: Storage of cowpeas under high temperature and high humidity (HTHH) condition leads to the development of “hard to cook” (HTC) defect. This results in very long cooking times. Heat pre-treatments before storage of cowpea seeds could be employed to reduce enzyme activity, believed to be responsible for this defect, during storage. We studied micronization and hot-air roasting as heat pre-treatments of seeds in controlling the HTC defect development. Micronization and hot-air roasting were done on pre-conditioned cowpea seeds prior to accelerated storage (40 days, 42oC and 80% RH). Samples were analysed for cooking time, phytase activity, phytate Content and soluble pectin Content. Structural changes to parenchyma cells were studied using microscopy. Micronization and hot-air roasting reduced cooking time of cowpeas after storage under HTHH conditions compared with control samples by 64% and 35%, respectively. Phytase activity was reduced by 45% and 70% by roasting and micronization, respectively. Reduced phytase activity was associated with higher phytate and soluble pectin Contents in micronized samples than in roasted samples after HTHH storage. Microscopy revealed tri-cellular junctions with intact cellular structure in the control cooked sample after storage, indicating that there was minimal alteration in the middle lamella. Treated samples had less distinct tri-cellular junctions indicating some degree of solubilization of the middle lamella. Micronization was a better heat pre-treatment than hot-air roasting in controlling the development of HTC defect of cowpeas during HTHH storage