Development of Protein Enriched Maize - Cassava Leaf Composite Extruded Instant Porridge Flour

Abstract

Food insecurity and malnutrition especially protein deficiency is a major public health problems in developing countries. The aim of this study was, therefore to develop protein-enriched extruded instant porridge flour using composite flour of maize and cassava leaf through microbial fermentation and extrusion cooking technology. Microbial fermentation using starter cultures of Lactobacillus plantarum, Saccharomyces cerevisiae and their co-cultures were used particularly to assure the safety of ingredients. Hence, these starter cultures showed a significant improvement in the nutritional qualities of maize flour and cassava leaves by reducing the anti-nutritional factors, particularly the hydrogen cyanide level in cassava leaves below the threshold limit (HCN < 10 mg/kg). Response Surface Methodology (RSM) in Box-Behnken design was used for formulation and optimization of the process variables for the production of protein-enriched instant flour. There was a significant (p < 0.001) increase in the protein and essential amino acid contents of the extruded flour due to the supplementation of maize with cassava leaf flour. The optimum extrusion variables that could give an optimum proximate composition and essential amino acid profiles were at extrusion temperature (118oC), feed composition (8%) and feed moisture (14%) with composite desirability of 99.8 per cent. The water solubility index showed a significant (p < 0.05) positive correlation between in vitro protein digestibility and mineral contents. In vitro protein digestibility was significantly (p < 0.05) increased by extrusion temperature and feed composition. The descriptive panel developed a lexicon of 12 attributes to profile the product's appearance, aroma, flavour, taste and texture. In comparison to the control, the inclusion of cassava leaf flour increased the intensity of bitterness by up to 59% and the number of specks by up to 46%. The control sample had the highest consumer acceptability score for all the attributes followed by instant porridge developed at a feed composition of 5%, feed moisture of 14% and extrusion temperature of 100oC. Paper packaging material had higher scores for desirable attributes such as overall aroma and sweetness while low-density polyethylene had a higher score for undesirable attributes such as bitterness and rancid off-flavours. Production of protein-enriched foods from locally available ingredients can be an ideal solution for the ever-increasing food and nutrition insecurity particularly protein-energy malnutrition in developing countries. In this study, the use of cassava leaf and maize composite flour for the production of protein-enriched flour through the application of extrusion technology has been found ideal for protein and other micro-nutrient improvements.