Influence of fermentation and germination on some bioactive components of selected lesser legumes indigenous to Nigeria

Abstract

This study assessed the effects of fermentation time (2, 3 and 4 days) and germination time (2, 3 and 4 days) on total phenolics, tannin, anthocyanin, carotenoids and flavonoids contents of lesser legumes: cowpea (Vigna unguiculata L.), bambaranut (Vigna subterranean L.), red bean (Phaseolus vulgaris), pigeonpea (Cajanus cajan), African breadfruit (Treculia africana) seeds, African yam bean (Sphenostylis stenocarpa) seed, African oil bean (Pentaclethra mycrophylla Benth.) seed and groundnut (Arachis hypogea L.). The antioxidant and reducing powers of a three day germinated samples were also evaluated. The result revealed that fermentation reduced the total phenolics, tannin, anthocyanin, carotenoid and flavonoid contents of the samples with increasing fermentation time; however, red bean showed minimal increase with increasing fermentation time. There was significant (p < 0.05) increase in the total phenolics of all the samples with increasing germination time but, tannin and flavonoid showed significant (p < 0.05) reduction with increasing germination time. Germination significantly (p < 0.05) reduced the carotenoid and anthocyanin levels in all the samples, however, red bean, pigeonpea and African oil bean showed increases with increasing germination time. Samples evaluated exhibited significantly (p < 0.05) different antioxidant capacities. African oil bean and groundnut had the highest antioxidant activities 52.18% and 52.16%, respectively while, African yam bean seed was the lowest (19.85%). Similar trend was observed in the reducing power of the raw samples where groundnut, bambaranut and African breadfruit showed significantly (p < 0.05) higher reducing power. Three (3) days germination significantly (p < 0.05) increased the antioxidant capacities by 14.65%, 18.42%, 53.58%, 52.84%, 17.24%, 14.56%, 53.18% and 43.03% in African oil bean, bambaranut, cowpea, red bean, African breadfruit, groundnut, African oil bean and pigeonpea, respectively. Therefore, for increase antioxidant activity in lesser known legumes, germination is more preferred over fermentation and for maximum yield of total phenolics, three and four days germination time are recommended