Hydrothermal treatments affect the development of the hard‐to‐cook defect in cowpeas

Abstract

Abstract The hard‐to‐cook defect is a well‐known problem in stored legumes, including cowpeas, which reduces the consumption and utilization of these nutritious foods. It is a generally held view that the enzyme, phytase is involved in the development of the defect. The effectiveness of steam treatments in preventing the characteristic hardening of cowpeas stored under unfavorable conditions was investigated. The factors considered were steaming temperature (100°C, 121°C), steaming time (2, 4, and 6 min) and initial seed moisture content (13%, 20%). The treated cowpeas were stored at either 4°C (no relative humidity [RH] control) or 42°C/80%RH. The texture of cooked treated cowpeas was comparable with the control; the peak forces were 504–639 N and 616 N, respectively, for treated and control cowpeas before storage. Although the treatments reduced the texture of cooked cowpeas prior to storage, only steaming at 121°C for 4 or 6 min prevented hardening during storage. Steaming reduced the phytase activity of cowpeas to 53%–64% of original activity; however, a significant increase occurred with storage. Steaming and storage significantly decreased water absorption from 91.28 g/100 g to 75.68–88.02 g/100 g after 24 h soaking. A decrease in phytate content and increases in electrolyte leakage and pectin loss were also recorded. A lack of significant correlation between cooked bean hardness and the physicochemical indices implies that the improved texture of cooked treated cowpeas occurred through a pathway not typically associated with the development of the hard‐to‐cook defect in cowpeas.

Keywords

• cowpeas
• hard‐to‐cook
• moisture content
• phytase
• steam treatment
• storage