Bioactive profile of borno brown Vigna unguiculata grains as influenced by pre-harvest synthetic chemicals

Abstract

This study investigated the impact of pre-harvest synthetic chemical treatments on the post-harvest bioactive contents, pasting, colour, and thermal properties of borno brown V. unguiculata (L.) Walp grains. Seeds of borno brown V. unguiculata (L.) Walp was planted on an already ploughed, harrowed and ridged plot of land with a portion cultivated as organic and another non-organic. After 90 days, mature grains were harvested and analyzed using standard procedures. Results showed that a total of 44.33 g bioactive compounds/100g grain was present in the organic borno brown V. unguiculata grains whereas, 20.56 g bioactive compounds/100g grain was present in the non-organic (control). The identified bioactive compounds in the organic grains included [heneicosane (4.50g/100g grain)]; [12-Methyl-E,E-2,13-octadecadien-1-ol (4.09/100g grain)]; [3-(2-Hydroxy-6-methylphenyl)-4(3H)-quinazolinone (7.40 g/100g grain)]; [Methaqualone (9.08 g/100g grain)]. The non-organic contained [heneicosane (4.07g/100g grain)]; [3-(2-Hydroxy-6-methylphenyl)-4(3H)-quinazolinone (5.09 g/100g grain)]; [Methaqualone (10.61 g/100g grain)]. Flavonoids, alkaloids, total phenolic, 2,2-diphenyl-1-picryl-hydrazl (DPPH) and ferric ion reducing antioxidant power (FRAP) contents of the organic grains were 19 mgRE/100g, 3.40 mg/100g, 1550 mgGAE/100g, 2840 μmolTEAC/100g, and 20.08 mmol Fe2+/100g, respectively. The non-organic grains had flavonoids (11.31 mgRE/100g), alkaloids (1.86 mg/100g), total phenolic (1110 mgGAE/100g), DPPH (1779 μmolTEAC/100g) and FRAP (12.24 mmol Fe2+/100g). The peak viscosity of 111.52 RVU, final viscosity (141.25 RVU) and pasting temperature (82.01 °C) were obtained for the organic grains while non-organic had peak viscosity of 93.10RVU, final viscosity (95.20 RVU) and pasting temperature (80.10 °C). The colour parameters L*, a*, b* and ΔE were 73.10, 0.68, 14.47 and 12.98 for the organic and 84.25, 0.30, 21.10, and 0.00, respectively for non-organic grains. The thermal property showed enthalpy (ΔH) and peak temperature (Tp) of 3.12 J/g and 78.25 °C for organic, and 2.14 J/g and 76.28 °C for non-organic grains, respectively. Phenolic compounds profile showed that organic grains were richer in epicatechin, gallic acid, ferulic acid, chlorogenic acid, 4-hydroxy benzoic acid, and catechin. Organic grains showed significant (p < 0.05) superiority in bioactive compounds, phytochemicals, and antioxidants over non-organic grains. Good pasting properties of the organic grains showed that it could function as a food thickener. Organic borno brown V. unguiculata grains are rich in health-promoting compounds and could, therefore, be used as an ingredient in the development of functional foods.