Physicochemical properties of instant noodles produced from blends of sweet potato, soybean and corn flour

Abstract

Studies on substitution of wheat partially with other composite flour and analysis on their different characteristics had been reported; but there was a need to optimize both the formulation and process conditions to give optimum quality while substituting wheat wholly with composite blends of other flours. This study investigated the formulation of instant noodles made from blends of sweet potato, corn, soybean flours; with the quantity of water. The impact of baking temperature, mixing time, frying time and frying temperature on noodles quality were also investigated. Investigations were conducted employing a four-component constrained D-optimal mixture-process experimental design with 39 randomized experimental runs. The formulation design constraints were sweet potato flour (10% ≤ x1 ≤ 61%), soybean flour (5% ≤ x2 ≤ 20%), corn flour (5% ≤ x3 ≤ 30%), and water (25% ≤ x4 ≤ 37%). Other components of the formulation were salt (2.5%), sodium carbonate (0.5%), guar gum (0.5%), and soy lecithin (0.5%). The processing factors investigated were mixing time (2 mins ≤ z1 ≤ 10 mins), frying time (1 min ≤ z2 ≤ 3 mins), and frying temperature (140°C ≤ z3 ≤ 160°C). The D-optimal mixture-process design was used to evaluate the effect of changes in mixture compositions and the three processing factors on the main proximate qualities of the formulated instant noodles. The effects were established through analysis of variance at 5% level of significance. The formulated samples were evaluated for the proximate properties. From the numerical optimization through the desirability function, the formulation that produced noodles of highest desirability index of 0.723 was: 23.305% of sweet potato flour, 28.529% of soya bean flour, 18.021% of corn flour, 26.145% water, 2.749 mins mixing time, 1.35 mins frying time, and 140°C frying temperature, The proximate composition of this optimal formulation were: 13.17% moisture content, 6.616% ash content, 22.862% crude protein, and 37.707% energy value, 16.001% crude fat, and 4.643% crude fibre.