Optimizing the formulation for production of orange fleshed sweet potato-based composite flour with grain amaranth, biofortified bean and maize flour

Abstract

Composite flours are an effective way to improve the nutritional intake of vulnerable populations, ensuring that essential nutrients are delivered through culturally acceptable, affordable, and locally available food sources. Orange fleshed sweet potatoes can significantly boost the nutritional quality of composite flours by adding essential nutrients making them a powerful tool in fighting malnutrition and improving health outcomes for vulnerable populations. The aim of this study was to develop a protocol for production of nutrient enhanced orange fleshed sweet potato based composite flours and assess their potential as ingredients in porridge making. I-optimal design of design expert software was used to generate twenty (20) experimental runs. Extrusion cooking was carried out using a twin-screw extruder at a barrel temperature of 60, 120 and 150 ℃, screw speed of 350 rpm and feed moisture of 5%. The developed composite flours (raw and extruded) and commercial flour as control were analysed for proximate composition, functional properties, pasting properties and phytochemicals content. Porridges prepared from four optimized formulations were compared to one made from a commercial composite flour (control). Samples were evaluated by 50 consumers (26 females, 24 males) using a 9-point hedonic scale for sensory acceptance and a 5-point Likert scale for willingness to buy. Principal component analysis (PCA) was conducted to understand the relationship between sensory attributes and consumer’s overall liking. The obtained results showed that bulk density significantly decreased from 0.776 to 0.515 g/ml, and was highest in the commercial flour (control) and least in extruded formulation (EF2). The highest water absorption capacity (528.57%) and oil absorption capacity (295.13%) were found in extruded formulations EF1 and EF2 respectively, whereas the least water absorption (227.71%) and oil absorption capacity (187.64%) were found in the commercial flour. The highest water absorption index (5.40 g/g) and water solubility index (57.81%) were observed in RF1 and EF2 respectively. Extruded blends EF1 and EF2 had the highest solubility (64.22 and 66.19%) respectively, whereas the swelling power was high (10.74 and 8.55%) in raw blends RF1 and RF2 respectively. There were significant (p< 0.05) differences in moisture, protein, dietary fibre, ash, fat, carbohydrates and gross energy. The moisture content and crude fat ranged from 7.72 to 5.84% and 5.65 to 2.30% respectively, whereas crude protein, total dietary fibre, ash and carbohydrates ranged from 15.45 to 18.16%, 0.46 to 4.04%, 1.39 to 3.81% and 79.02 to 86.87% respectively, and the gross energy varied between 427.74 and 437.75kcal. The peak, trough, breakdown, final and setback viscosities varied significantly (p< Ugx 5000 for a kilogram extruded flour composite flour (EF2) and between 5000 and 10000 for a kilogram of the raw composite flour (RF2). Results on properties of developed OFSP-based composite flour reveal that it is nutritionally superior to the commercial flour (control) on the market.