Utilization of orange fleshed sweet potato and bio-fortified beans for the production of nutritionally enhanced noodles.

Abstract

Processed foods have become an important part of the diet of most people and their consumption is on the rise globally. Consumers are increasingly embracing processed foods, mainly because they are convenient, tasty, attractive, accessible, safe, and affordable. Food processing leads to the creation of diversity of food products and contributes to curbing food loss, enhancing sensory properties of food and increasing food affordability. Despite the increasing popularity and convenience of processed foods, some, like noodles, are largely over refined and low in nutrients. The objective of this study was to develop a protocol to produce nutrient enriched noodles with orange-fleshed sweet potato (OFSP) puree and biofortified bean powder as ingredients and evaluate their quality parameters. Response surface methodology (RSM), using Design Expert software was used to determine the best formulation and optimal processing conditions for producing the noodles. Independent variables included the content of wheat flour, OFSP, and bean powder, as well as dough thickness, drying temperature, and time while dependent variables included hardness, moisture, protein, dietary fibre, iron, and zinc content. A total of 68 runs were generated, and products analyzed. The hardness, moisture, protein, dietary fibre, iron, and zinc content of noodles made using the different runs were found to range from 0.1 to 26.5 N, 6.1 to 35.9 %, 7.8 to 34.5 %, 2.4 to 22.1 %, 11.1 to 84.9 ppm, and 20.6 to 59.1 ppm, respectively. Reduced quartic models were found to adequately represent relations between data for the different variables with R2 values of 0.90, 0.99, 0.95, 0.90, 0.86, and 0.96 respectively. All the models had a non-significant lack of fit (p > 0.05). The optimal protocol to produce nutrient enhanced noodles was determined to consist of a formulation containing 73% wheat, 21.5% OFSP, and 5.5 biofortified bean; dough thickness of 2.0 mm; drying temperature and time of 80.0 ℃ and 143.4 minutes, respectively. These conditions yielded noodles with 5.9% moisture, 11.0 N hardness, 34.5% protein, 11.9% dietary fiber, 86.9 ppm iron, and 50.53 ppm zinc with a desirability function of 0.82. On validation, there was no significant difference (p > 0.05) between experimental and predicted values. The results obtained revealed that the nutrient enhanced noodles contained significantly higher ash, protein, dietary fibre, iron, zinc, and beta-carotenoid content (greater by 1.6 %, 20.3 %, 2.0 %, 83 ppm, 47 ppm, and 0.5 mg/100g respectively) as compared to noodles made from 100% plain wheat flour. The noodles hardness reduced when part of wheat was substituted with OFSP puree and BFB flour, and they had good cooking properties with cooking loss below 10%. The colour was brighter in comparison to the control noodles. The findings of this study showed that it is technically feasible to produce nutrient enhanced noodles using OFSP and biofortified beans, which are abundant in Uganda and other parts of Africa. Production of noodles using these raw materials would contribute to creation of markets for raw materials, import substitution and improved nutrient intake by their consumers.