Physicochemical, in vitro starch digestibility and sensory characteristics of biofortified yellow maize-cowpea composite flours and biscuits

Abstract

AbstractThe consumption of whole grain cereals, pulses and their products, such as biscuits, is associated with protection against nutrition-related non-communicable diseases. Hence, the aim of this study was to evaluate the physicochemical qualities and in vitro starch digestibility of flours and biscuits formulated with biofortified yellow maize (M-f) and cowpea (C-f) composites, as well as the biscuits’ sensory attributes. Biscuits, coded M-b, MC-b1, MC-b2, MC-b3, and C-b, were baked from composite flours of M-f and C-f (M-f:C-f, w/w) at the proportions of 100:0, 75:25, 50:50, 25:75, and 0:100, respectively. Refined wheat flour (W-f) and its biscuit (W-b) served as controls. Individually, the final viscosities of M-f (157.36 RVU) and W-f (159.12 RVU) were comparable (p > 0.05); but both were significantly higher (p < 0.05) than that of C-f (93.15 RVU). Among the composite flours, MC-f2 and MC-f3 had the highest final (175.43 RVU) and peak (65.52 RVU) viscosities, respectively. The total carbohydrate, crude fat, and energy value increased significantly (p < 0.05) with increasing proportion of M-f in the composite flours and biscuits, while the crude protein and ash contents increased with an increasing proportion of C-f. The ranges of total carbohydrate, crude fat, and food energy in the biscuits were 51.03 (C-b) - 68.27% (W-b), 12.15 (W-b) - 19.02% (M-b), and 414.33 (C-b) - 455.91 kCal/100 g (M-b), respectively. The concentrations of starch, amylose, amylose/amylopectin ratio, starch hydrolysis index (HI), as well as estimated glycaemic index (eGI) of the composite flours and biscuits decreased significantly with an increasing proportion of C-f. Thus, the ranges of starch and eGI in the biscuits were 41.02 (C-b) - 68.01% (W-b) and 34.99 (C-b) - 57.19% (W-b), respectively. Crude protein (r = − 0.715, − 0.696), starch (r = 0.966, 0.954), amylose (r = 0.947, 0.931), and amylopectin (r = − 0.947, − 0.931) significantly correlated with eGI and HI, respectively. The sensory acceptability of the composite biscuits improved as the proportion of C-f increased. Hence, it is concluded that increasing the level of cowpea in biofortified yellow maize-cowpea composite flours and biscuits enhanced their physicochemical and sensory attributes, and reduced their estimated GI. Graphical Abstract