Protein iron and zinc content and bioaccessibility of a ready-to-eat sorghum and cowpea meal developed for 2-to 5-year old African children

Abstract

Protein, iron and zinc deficiencies are among the most prevalent nutritional deficiencies among children under the age of five years living in developing countries. Nutritional deficiencies are caused by insufficient dietary intake due to food insecurity. Sorghum and cowpea are important staple plant foods indigenous to Africa. They are inexpensive sources of protein, iron and zinc. Hence, they are suitable vehicles that could be used for improving nutrition in young children. Their use is, however limited by the long cooking time required for their preparation and the restricted types of food products available for young children. A ready-to-eat (RTE) composite meal suitable for young children aged two to five years was formulated using extrusion cooked decorticated sorghum (ES) and micronised (infrared treatment) dehulled cowpea (MC) to make an ESMC RTE meal. The ESMC RTE meal was supplemented with a cooked cowpea leaf relish. The study investigated the effects of the high temperature short time (HTST) (extrusion cooking and micronisation) heat treatments, compositing and adding a cooked cowpea leaf relish on the protein, iron and zinc contents; trypsin inhibitor activity (TIA), total phenolic content (TPC), tannins and phytate contents. The study also compared the effects of HTST heat treatment, compositing and adding the relish on protein quality, in vitro protein digestibility (IVPD) and in vitro iron and zinc bioaccessibilities against raw sorghum and cowpea, the raw composite and a commercial fortified corn (maize): soy RTE porridge. Assessments for protein quality were: calculated Protein Digestibility Corrected Amino Acid Score (PDCAAS), pepsin and multienzyme IVPD assays for IVPD and dialysability assay for in vitro iron and zinc bioaccessibilities. A mineral solubility assay was used to estimate iron and zinc bioaccessibility. Micronisation inactivated TIA and instantised the cowpea flour resulting in excellent hydration properties. A daily serving of the recommended portion size of the ESMC RTE meal with cooked cowpea leaf relish would meet approximately 40% of the protein and lysine requirements for children aged two to five years. Further, the calculated PDCAAS would be similar to the commercial fortified RTE porridge. This was despite the negative effect on protein digestibility of the high tannin content in cooked cowpea leaf relish. A recommended serving of ESMC RTE meal with cooked cowpea leaf relish could contribute ?85 and 18% towards children s iron and zinc recommended dietary allowance, compared to the commercial fortified RTE porridge (84 and 125%, respectively). However, the higher iron and zinc bioaccessibilities of the ESMC RTE meal with cooked cowpea leaf relish compared to the commercial fortified RTE porridge (11.8 vs. 5% and 18.9 vs. 2.7%) resulted in higher and similar levels of bioaccessible iron (2.24 vs. 0.86 mg/100 g, db) and zinc (0.35 vs. 0.32 mg/100 g), respectively. Thus, the ESMC RTE meal with cooked cowpea leaf relish compared to the commercial fortified RTE porridge would provide more available iron and similar levels of zinc towards the basal requirements of children. This ESMC RTE meal with cooked cowpea leaf relish can provide protein, iron and zinc nutrition for young children, increase diversity and food security in Africa.