Novel Vigna subterranea (L.) Verdc Soluble Dietary Fibre-Starch Nanocomposite: Functional and Antioxidant Characteristics
1Department of Food Science and Technology, Cape Peninsula University of Technology, P.O Box 1906, 7535 Bellville, South Africa
2Department of Chemical Engineering, Cape Peninsula University of Technology, P.O Box 1906, 7535 Bellville, South Africa
Received: 6 July 2021
Accepted: 25 May 2022
bambara groundnut; starch; dietary fibre; nanocomposite; antioxidants; pasting properties
Research background. Bambara groundnut (BGN) (Vigna subterranea [L.] Verdc.) is a source of soluble dietary fibre (SDF) and starch, making it a great source of the two polysaccharides. Bambara groundnut soluble dietary fibre (BGN-SDF) is rich in bioactive compounds, namely, uronic acids (11.8 %) and hydrolysable polyphenols (20 mg Gallic acid equivalent (GAE)/g), with crucial physiological and functional benefits. The industrial use of native starch is limited because of the inherent undesirable attributes that render it unstable. The aim of this study is to characterise the antioxidant, functional and physicochemical properties of bambara groundnut starch-soluble dietary fibre nanocomposite (STASOL).
Experimental approach. The pasting properties by rapid visco analysis (RVA), chemical composition following AOAC procedures, hydration properties, oil binding capacity (OBC), emulsion activity index (EAI), emulsion stability index (ESI) and antioxidant properties of bambara groundnut starch (BGNS), BGN-SDF and STASOL were studied.
Results and conclusions. BGN-SDF and STASOL did not exhibit typical pasting properties. STASOL was high in carbohydrates (78.69 %) and proteins (6.96 %), low in fat (0.84 %) and had a considerable amount of ash (4.88 %). BGNS, BGN-SDF and STASOL showed significant (p<0.001) differences in solubility. The EAI of BGNS, BGN-SDF and STASOL were 23.25, 85.71 and 90.65 %, respectively, and the ESI of BGNS, BGN-SDF and STASOL were 23.33, 87.13 and 87.49 %, respectively. The three biopolymers differed significantly (p<0.001) in all colour characteristics; lightness (L*), redness/greenness (a*), yellowness/blueness (b*), chroma and hue angles. The polyphenolic content of BGNS, BGN-SDF and STASOL was 0.10, 6.59 and 0.46 mg GAE/g, respectively, and their ferric reducing antioxidant power (FRAP) values were 1.16, 4.77 and 1.45 μmol ascorbic acid equivalents (AAE)/g, respectively. The phenolic compounds, chlorogenic acid (18 mg/g), monocrotaline (20 mg/g), luteolin 7-O-(6''-malonylglucoside) (4 mg/g) and casuarine 6-alpha-D-glucoside (27 mg/g) were present in BGN-SDF but absent in BGNS and STASOL. STASOL possesses desirable physicochemical and antioxidant properties, making it suitable as an ingredient in various food systems.
Novelty and scientific contribution. Nanocomposites have the potential to revolutionise the food industry but their study as food ingredients is very limited. Furthermore, nothing is known about the physicochemical, functional and antioxidant characteristics of STASOL. Investigating these properties of STASOL will address this knowledge gap.