Proximate, antinutritional and characterization of volatile components of African yam bean (Sphenostylis stenocarpa) flour

Abstract

African yam bean (Sphenostylis stenocarpa) is a legume cultivated primarily for its edible tubers, which look like elongated sweet potatoes, and for its seeds, which are contained in hard and tough long pods. It has potential to increase food security because of its nutrient composition though still classified as Neglected and Underutilized Species (NUS). Different processing methods (fermentation, boiling, toasting) were used in African yam bean (AYB) flour production. This study evaluated the proximate and antinutrient composition of the AYB flour samples using standard methods. The volatile profile of the AYB flour samples were determined using Gas - Chromatography/Mass – Spectrometry (GC-MS). There were significant differences in the results of the proximate and antinutrient analysis of the AYB flour analysis. The fermented AYB flour samples had the highest protein content of 23.20 % while the lowest protein content was recorded by the boiled AYB sample (19.43 %). Fermentation increased the protein and ash levels in the processed AYB flour samples (23.20 and 2.97 %). Carbohydrate content of the fermented AYB flour sample was lowest (58.85 %) compared to the other samples (60.46 – 65.16 %). Boiling and fermentation reduced the antinutrient contents of the processed AYB flour samples. A total of 152 volatiles were identified thus consisting mostly of amines and esters followed by alcohols, nitrogen-containing compounds, ketones, acids and others. The total area count was highest in toasted AYB flour sample (amines) while lowest in fermented AYB sample (ketones). Benzenamine, 2, 6 –dichloro was the predominant volatile compound. Fermentation reduced ketones (0.2362 %) and increased alcohols (2.0787 %), acids (1.4997 %), esters (1.6777 %) and nitrogen-containing compounds (4.945 %) while boiling increased the number of ketones (1.6984 %) in the AYB flour samples. The results of this study will help in food product value addition and innovation which will help improve food security and health of the populace.