Nutritional and Antioxidant Properties of Resistant Starch-Based Flour Blends from Unripe Plantain, Pigeon Pea and Rice-Bran

Aim: The nutrients and antioxidants of blends of native resistant starch, acetylated resistant starch, and flours of unripe plantain, pigeon pea and rice bran were investigated as possible alternatives to functional food products in managing type-2 diabetes. Place and Duration of Study: Food Chemistry Laboratory, Department of Food Science and Technology, and Functional Foods Laboratory, Department of Biochemistry, Federal University of Technology, Akure, Nigeria. From January, 2022 to January, 2023. Methodology: Native resistant starch was isolated from plantain and was modified via acetylation. Five sample blends of native resistant starch, acetylated resistant starch, and flours of pigeon pea and rice bran were prepared, using Mixture Design Expert 11.0.0 and were coded as follows: PLF – (100% Plantain flour), used as a control sample; PLPRF – plantain flour: pigeon pea flour: rice bran flour (73.08:15.15:11.76); PSPRF – native plantain starch: pigeon pea flour: rice bran flour (73.08:15.15:11.76); AP1SPRF – acetylated plantain starch: pigeon pea flour: rice bran flour (73.08:15.15:11.76); AP2SPRF – acetylated plantain starch: pigeon pea flour: rice bran flour (70.67:18.15:11.18). The proximate compositions, minerals, amino acid profiles, α-amylase and α-glucosidase and in-vitro antioxidant potentials of the samples were compared with the commercial flour product, CRF (100% Cerolina flour: wheat and soybean produced by More Foods Lagos, Nigeria). Results: The results showed that AP2SPR had the lowest moisture content (2.40%), highest ash content (4.63%) and lowest fat content (2.42%). K, Cu, Fe. Na, Zn and P were more relatively abundant in the blends than in PLF. Generally, the chemical compositions of the flour blends improved with the addition of quality protein, which extensively enhanced the mineral contents in terms of Ca, K, Fe, Zn and P. Total essential amino acids were higher in PLF and the flour blends than CRF, ranging from 35.18 (g/100g protein) in CRF to 41.81 (g/100g protein) in PLPRF whereas their total non-essential amino acids showed an opposite trend, ranging from 58.18 (g/100g protein) in PLPRF to 64.84 (g/100g protein) in CRF. Upon acetylation, total essential amino acids improved from 39.84 (g/100g protein) in PSPRF to 41.00 (g/100g protein) in AP1SPRF and 41.32 (g/100g protein) in AP2SPRF. Both AP1SPRF and AP2SPRF were able to reduce Fe2+ to Fe3+, scavenge DPPH, FRAP and ABTS and inhibit α-amylase and α-glucosidase activities. Conclusion: The flour blends of AP1SPRF and AP2SPRF studied were a good source of resistant starch and bioactive ingredients that would be useful in a variety of dietary functional food products to manage type-2 diabetes.