Physico-chemical and nutritional properties of maize-cowpea composite gluten-free pasta manufactured by extrusion cooking

Abstract

In sub-Saharan African countries, rapid urbanization has resulted in more people resorting to a diet of convenience as well as fast food characterised as energy-dense with saturated fat, sodium, sugar and low fibre. This food consumption pattern has been associated with development of diet-related non-communicable diseases such as obesity and diabetes. As a result, a search for new types of raw materials that can provide nutritious and healthier options for convenience foods has increased. The objective of the study was to determine the effects of extrusion cooking and compositing with whole grain cowpea flour on the nutritional and functional properties of maize pasta with the aim of producing a convenient nutrient-dense pasta using locally available and indigenous grains. The nutritional and functional properties of the pasta made with different maize and cowpea ratios (100% cowpea flour, 50% cowpea flour: 50% maize flour, 30% cowpea flour: 70% maize flour, 100% maize flour) were analysed in reference to commercial 100% rice pasta. Addition at 30% and 50% of cowpea flour in the composites to maize pasta and the 100% cowpea flour pasta, increased leaching of material, and stickiness but decreased water absorption, firmness and cooking time of the pasta compared to maize pasta alone. 100% cowpea flour pasta had the shortest cooking time of three minutes and rice pasta had the longest cooking time of ten minutes. Increasing the level of cowpea flour in the composites increased the level of protein, amount of digestible protein and dietary fibre (soluble and insoluble) in the pasta compared to the reference pasta.However, starch digestibility of the pasta samples significantly (P<0.05) decreased with an increase in the level of cowpea flour at 30%, 50% and 100%. Differential scanning calorimetry showed that amylose-lipid complexes were formed during extrusion cooking of the pasta. Confocal laser scanning microscopy showed that with an increase in cowpea flour in the pasta samples, there was an increase in stained fluorescing red spots. Scanning electron microscopy also showed what could likely be starch granules embedded in the protein network. Usage of increased levels of cowpea flour in composites with maize flour in the production of a gluten-free pasta improved the protein quality and fibre content of the gluten-free pasta. The addition of cowpea flour in cereal-based pasta could potentially provide a good source of dietary protein and fibre.