Functional and Microstructural Characterisation of Bambara Groundnut (Vigna Subterranea) Starch as Affected by Varying Degrees of Succinylation

Abstract

Bambara groundnut (Vigna subterranea) is an under-exploited pulse rich in starch. Scientific data about the impact of varying degrees of succinylation on its starch content are sparse. Amidst the rising demand for such modified starch variants, bridging this information gap is necessary. Isolated starch from Bambara groundnut seeds was succinylated (2-14g succinic anhydride /100g starch extracted) and thereafter the degree of succinylation was evaluated. Physicochemical, functional, and microstructural characteristics of native and succinylated variants of the Bambara starch (SBS) were investigated using established procedures. Amylose content increased marginally (av.17%) among some samples. Water and oil absorption capacities peaked at 2.498 and 0.7185g /g of starch respectively. Pasting viscosities (5682-7025.5cP) increased irrespective of the order of substitution. X-ray diffract grams indicated an increase in crystallinity (A-type) with a strong peak at approximately 23o (2ϴ). This was however lost at higher treatment levels. FTIR spectra of the starches reflected a typical absorption band of a starch backbone. Scanning electron micrographs of succinylated starches were generally oval, exhibiting surface cracks sizes (13.55-44.25µm). Succinylated Bambara groundnut starches at low treatment levels (2-4%) may prove valuable in soups and gravies requiring a high viscosity, stability, and clarity. At higher treatment levels, non-food applications may just be the right outlet.