Effect of infrared heating of pre-soaked whole and dehulled bambara groundnut (Vigna subterranea) seeds on their cooking characteristics and microstructure

Abstract

Bambara groundnut seed is an indigenous legume with good protein quality. However, the cooking time (3 h) has contributed to its under-utilisation. In this study, the effects of pre-soaking bambara groundnut seeds with or without dehulling (whole and dehulled), followed by infrared heating (130 °C, 0, 5, 10 and 15 min) on their cooking characteristics were studied. As infrared heating time increases (0, 5, 10 and 15 min), soluble pectin increased and cell wall separation was enhanced in the grains. Water absorption during soaking and cooking (whole and dehulled) were higher in infrared heated samples compared to untreated. The rate of water absorption during cooking (95 °C) was higher in pre-soaked whole and dehulled bambara groundnut after infrared heating treatment for 15 min compared to untreated seeds. Further, the cooking times of untreated whole (162 min) and dehulled (41 min) was reduced to about 60 min and 30 min respectively after infrared heating of pre-soaked seeds for 15 min. With or without dehulling, infrared heating especially at 15 min can produce bambara groundnut seeds with short cooking time limiting energy demand in both urban and rural communities in Africa.