Nutritional evaluation, microstructural properties and sensory evaluation of instant complementary porridge developed from malted finger millet and soybean flour

Abstract

Finger millet (FM) grains are regarded as gluten-free, low-cost, and climate-resilient crops. Despite these advantages, their protein quality is limited, which restricts their suitability as a sole complementary instant porridge. Soybean (SB) flour, an inexpensive source of high-quality protein compared with animal protein, was incorporated to improve the nutritional balance. Complementary instant porridge was selected as the study product because of its widespread use in infant feeding, where convenience, affordability, and nutritional adequacy are critical. This study examined the nutritional, microstructural, antioxidant properties, and sensory evaluation of finger millet complementary instant porridges (light and dark brown) supplemented with soybean flour. Ten distinct samples were formulated by blending malted FM flour and soybean flour at 100%, 90:10%, 80:20%, 70:30%, and 60:40% (light & dark brown: soybean). The unmalted light and dark brown FM flours were used as control (light brown flour and dark brown flour (LBF & DBF) The pasting, thermal, microstructural, and functional properties of malted FM flour were analysed. The proximate composition, mineral content, amino acid profile, antioxidant properties, colour attributes, and sensory analyses of the malted FM-SB instant complementary porridges were determined. Supplementation of SB flour improved the water absorption, oil absorption, and swelling capacities of the FM flours. Moreover, SB supplementation significantly increased cold paste viscosity and decreased cooked paste viscosity for both FM varieties. Their values ranged from 16.67 to 18.99 cP (light brown) and 16.67 to 18.58 cP (dark brown) for the cold-paste viscosity, and from 1921.67 to 484.64 cP (light brown) and 1915.53 to 488.07 cP (dark brown) for cooked paste viscosity. The values of lightness (L *) and redness (a *) decreased as SB incorporation increased, reaching a minimum of 1.34 for samples containing 60% light FM and 40% SB flours, respectively. On the other hand, yellowness (b*) and total colour change increased with increasing SB flour. The pasting qualities of malted FM flours decreased significantly as SB flour levels increased. Increased supplementation with SB flour resulted in a significant increase in the thermal characteristics of FM flours. A varied array of functional groups was observed by Fourier transform infrared (FTIR) spectroscopy, with over 5 unique peaks. The scanning electron microscopy (SEM) results showed that as SB flour increased, the composite flours' microstructure became richer in protein bodies. Supplementing SB flour increased the protein, fat, ash, and energy content of FM porridges. The addition of SB improved the mineral content of instant porridges, with iron registering the highest values in both FM varieties (26.70% & 22.41%) and potassium recording substantially low values (278.62%). Amino acid content increased significantly with increasing SB supplementation. The incorporation of SB flour significantly decreased the total phenolic content of instant porridges with values ranging from 101.72 to 72.09 milligrams of Gallic Acid Equivalents per 100 grams (mg of GAE / 100 g) and 100.57 to 64.47 mg of GAE / 100 g) for light and dark brown. On the other hand, a rise was observed in total flavonoid content, 2,2-diphenyl-1-picrylhydrazyl (DPPH), and ferric reducing antioxidant power (FRAP). Samples containing 20% SB flour were ideal in terms of taste (6.44 & 6.58), samples containing 40% SB flour were favourable in terms of aroma (6.51 & 6.41), texture (6.28 & 6.14), appearance (6.82 & 7.12) and overall acceptability (6.42 & 6.76). The study demonstrates that a combination of SB and malted FM flours is needed to enhance the nutritional qualities of the complementary instant porridge.