Proximate, mineral and anti-nutritional compositions of raw and processed African Yambean (Sphenostylis stenocarpa) seeds in Cross River State, Nigeria
African yambean (Sphenostylis stenocarpa, Hochst. Ex A. Rich, Harms) is an indigenous legume in tropical Africa. This food crop legume is highly under-exploited and very little scientific information is available in literature. In this study, the chemical composition (proximate, minerals and anti-nutritional profile) of raw and processed African yambean (AYB) seeds was investigated. Seeds of brown seed coat landraces of African yambean were collected from various locations in the Northern part of Cross River State. The seed characteristics were noted and subjected to boiling and toasting for one hour and thereafter evaluated for proximate composition, gross energy, mineral and antinutritional properties. Results showed that boiling significantly (P<0.05) increased crude Protein (CP) (22.10%), ether extract (EE) (7.53%) and gross energy (GE) (5.23 Kcal/g) compared to the raw (21.61% CP, 5.12% EE and 4.88 Kcal/g GE) as well as toasted seeds (21.41% CP, 5.195 EE and 4.51 Kcal/g GE). Toasting significantly (P<0.05) increased nitrogen free extract (NFE) (50.65%) and ash values. Processing (boiling/toasting) had significant (P<0.05) effect on mineral composition (Ca, Mg, K, Na and Fe) of the seeds except for phosphorus. Boiling significantly (P<0.05) reduced phytate (0.68%), alkaloid (0.70%) and trypsin-inhibitor (0.08 IU/mg) contents. Results have shown that African yambean seeds are rich sources of nutrients but have low human preference for food. But have a high potential as an energy/protein source in livestock feeds. The boiled AYB seeds had highest CP, mineral and lowest in anti-nutrient contents. Hence, boiling was the preferred processing method for AYB seeds.
Keywords: Boiling, legume, nutrient profile, toasting, yambean