NUTRITIONAL QUALITIES OF SORGHUM, SOYBEANS AND ORANGE-FLESHED SWEET POTATO IN POTENTIAL MANAGEMENT OF MICRONUTRIENT DEFICIENCIES

Abstract

Infant require adequate complementary food from six months when breastfeeding becomes inadequate to satisfy their nutritional needs. In Nigeria, the common complementary food is cereals gruel which is low in protein and high in anti-nutritional factors that reduce the bioavailability of some micronutrients. Micronutrient deficiencies are widespread and a serious childhood dietary problem in developing nations. Iron, vitamin A, iodine and zinc deficiencies are of public health importance owing to widespread occurrence globally. One of the identified strategies to militate micronutrient deficiency is dietary intervention. The present study was to determine nutritional efficacy of complementary foods from sorghum, soybeans and orange- fleshed sweet potato using the familiar traditional processing method. Four diets were formulated from mixtures of sorghum, soybeans and orange-fleshed sweet potato using the mixture design of the Response Surface Methodology to optimise the best samples: UF2 – Unfermented sorghum (56%), soybean (17%) OFSP (27%), F2 – Fermented sorghum (56%), soybean (17%), OFSP (27%), UF3 – Unfermented sorghum (59%), soybean (31%), OFSP (10%), and F3 – Fermented sorghum (59%), soybean (31%), OFSP (10%). Formulated complementary foods, control (Cerelac) CT and basal diet were analysed using standard methods for proximate, mineral, antinutrients, antioxidants, amino and fatty acids composition, functional properties and microbial loads. Anthropometric measurements, protein digestibility and haematology indices of rats fed with formulated complementary foods, control and basal diets were determined using standard methods. Adsorption isotherms of the formulated flour blends were determined using the standard static gravimetric method. Data were analysed using descriptive statistics, ANOVA and New Duncan’s multiple range test. The protein of fermented blend samples were significantly higher (p<0.05) (F2-15.80%, F3-25.29%, ) than Ogi (a local complementary food) (7.09%) but the values were comparable to the control food sample CT (cerelac) (15.79%). The iron, zinc and vitamin A content of fermented blends were significantly higher (p<0.05) iron (F2;7.76 mg/100g, F3;7.16 mg/100g), zinc (F2;3.65 mg/100g, F3;2.89 mg/100g), vitamin A (F2;0.95 mg/100g, F3;0.76 mg/100g ) than unfermented blend samples, iron (UF2;4.15 mg/100g, UF3;4.36 mg/100g), zinc (UF2;2.43 mg/100g, UF3;2.64 mg/100g), vitamin A (UF2;0.88 mg/100g, UF3;0.66 mg/100g), but lower than that of ogi iron (0.26 mg/100g), zinc (0.08 mg/100g) and vitamin A (0.02 mg/100g). The anti-nutritional compositions of fermented blends, tannin (F2;0.73 mg/100g, F3;0.67 mg/100g), phytate (F2;0.70 mg/100g, F3;0.55 mg/100g), oxalate (F2;0.32 mg/100g, F3;0.41 mg/100g), saponin (F2;0.20 mg/100g, F3;0.17 mg/100g) and trypsin (F2;1.08 mg/100g, F3;0.93 mg/100g) were significantly lower than that of unfermented samples with tannin (UF2;0.86 mg/100g, UF3;1.09 mg/100g), phytate (UF2;0.95 mg/100g, UF3;0.85 mg/100g), oxalate (UF2;1.53 mg/100g, UF3-1.05 mg/100g), saponin (UF2;0.57 mg/100g, UF3;0.92 mg/100g) and trypsin(UF2;3.20 mg/100g, UF3;3.11 mg/100g). The bulk density of F3 (0.73 g/cm3) was higher than that of ogi (0.66 g/cm3) and CT (0.64 g/cm3). The total essential amino acids content of the fermented and the unfermented blends (F2-32.24 mg/100g, F3-33.60 mg/100g, UF2-28.89 mg/100g, UF3-31.66 mg/100g) were higher than that of ogi (28.40 mg/100g) and the arginine and histidine content of F3(6.02 mg/100g, 1.80 mg/100g) were higher than that of the control sample, CT (5.60 mg/100g, 1.72 mg/100g) The microbial load recorded in all the samples(UF2, UF3, UF4, F2,F3,F4,CT and ogi), were significantly lower than the permissible limits (<106 CFU/g). The adsorption isotherms of formulated flour blends were found to be type II (S-shaped), characteristic of high sugar products. The biological values (BV) ranged from 75.11% for UF2 to 78.44% for F3 with CT (cerelac) having the highest 93.48% while the corn starch had the lowest (33.84%). The weight gained by the rat fed on formulated diet ranged from 46.0 g in F2 to 77.3 g in F3, and these values were higher than those rats fed on ogi (7.0 g) and corn starch (3.3 g) but lower than those of the control sample, cerelac (92.25 g). Iron, zinc and vitamin A values of rats fed on F3 were the highest followed by cerelac, the control sample (CT). Rats fed on sample F3 and cerelac (control sample) had high concentration of packed cell volume (PCV), haemoglobin concentration (HBC), red blood cell (RBC) and lymphocytes values of the urea nitrogen and the creatinine of the rats fed on the formulated diets, starch, ogi and ceralac ranged from 3.58 to15.32 mg/dl and 1.56 to 6.15 mg/dl respectively. Adsorption isotherms of the formulated flour blends were determined at the temperatures of 25 oC, 30 oC and 40 oC under 0.1 to 0.9 water activity (aw). The monolayer moisture content of sample F3 for GAB model at 25 oC, 30 oC and 40 oC were 0.021, 0.018 and 0.058 respectively while that of BET model were 0.010, 0.024 and 0.016 respectively. It was established that F3 food sample compared favourably with cerelac and was rated best in terms of micronutrient and protein quality. The study indicated good growth and development in rats fed with the formulated fermented diet F3, with no adverse effect on biochemical or haematological parameters and therefore can be recommended as an ideal complementary food to improve the nutritional status of children and help solve problems associated with deficiencies of micronutrients that are of public health importance i.e. Zinc, iron and vitamin A. Keywords: Micronutrient deficiencies, Formulated complementary foods, Adsorption isotherms, Cereal-legume-root based, Wister rats.