Nutrient Composition, Amino Acid Profile and Anti-nutritional Factors of Nixtamalized Maize Flour Supplemented with Sprouted Soybean Flour

Abstract

The high dependence on maize as a staple food in Tropical Africa, coupled with its low nutritive value necessitate investigation on how to improve the nutritional value of maize based foods. The present study was aimed at assessing the effect of supplementing nixtamalized maize flour with sprouted soy bean flour on the proximate composition, mineral content, amino acid profile and anti-nutritional factors in the blends. Nixtamalized maize flour was prepared by cooking maize grains in 1% unripe plantain peel ash solution (pH 10.2), steeped in the cooked solution for 15 h, washed, dried and milled into flour. The flour was supplemented with 0, 10, 20, 30 and 40% sprouted soy flour and analyzed for the aforementioned parameters. The results showed that protein, fat, ash, crude fibre and caloric value increased with increase in soy flour supplementation ranging from 9.26–22.57%, 4.51–10.53%, 1.38–2.06%, 2.14–2.39% and 408.47–434.85 kcal/100 g respectively while carbohydrate decreased from 82.71 – 62.45%. Potassium, calcium, magnesium and zinc contents increased from 267.58 – 286.35mg/100g, 126.93 – 161.03 mg/100 g, 135.71 – 163.81 mg/100 g and 4.52 – 4.85 mg/100 g respectively with soy flour addition. The total amino acids and total essential amino acids increased from 70.55 g/100 g protein and 30.54 g/100 g protein for the control to 87.97 g/100 g protein and 38.98 g/100 g protein for the 40% soy flour supplemented blends respectively. Limiting essential amino acids in both flours were significantly (P = 0.5) improved as a result of soy flour supplementation. Majority of essential amino acid chemical scores were above 100% except for lysine (51.03–66.38%), tryptophan (67.27–95.46%) and threonine (80.88 – 99.12%). Soy flour supplemented blends had higher phytate, trypsin inhibitor and tannin contents than the control sample but their values were low and may not have serious effect on nutrient bioavailability. The study clearly shows that nutritional value of nixtamalized maize flour can be improved by supplementing it with sprouted soy flour.