Oxidative storage stability of roasted marama beans (Tylosema esculentum)

Abstract

The marama bean is an underutilized traditional source of food for the indigenous population in Southern Africa such as the Herero, Tswana and Khoisan people and is mostly eaten as a snack after roasting in hot sand. The beans have a high content of protein and oil (mainly unsaturated lipid). This composition gives the marama bean a significant potential for production of various nutritious food products such as roasted beans. The aim of this study was to investigate the influence of different storage conditions on the oxidative stability of roasted marama beans. This was evaluated by packing the roasted marama beans in the presence or absence of oxygen and storing them with or without exposure to light for seven months. During the storage period, the changes in flavor related oxidation products (i.e. secondary oxidation products) were investigated. It was found that roasted marama beans should preferably be stored in darkness in bags containing a low amount of oxygen. Under these conditions the beans could be stored for at least five months without obtaining undesirable odors caused by lipid oxidation. Hexanal was found to be the limiting storage factor as it was the first volatile exceeding its odor detection threshold.