Effect of refining and supplementation on the viscosity and energy density of weaning maize porridges

Abstract

The study was undertaken to establish the extent to which use of refined maize flour in weaning porridges affects the viscosity and the energy density of the resulting porridges. Maize porridges from both refined and whole flours were made using modified traditional methods and the viscosity of the porridges was measured using a rotational viscometer. Other factors that might influence the viscosity outcome of the porridges such as flour concentration, supplementation with energy-rich foods, cooking time, temperature at the time of measurement simulating feeding temperature and shear speed were included at three levels per factor (low, medium and high) in a Central Composite Design. Overall, refined flour porridges had significantly (P ≤ 0.0001) higher viscosity than whole flour porridges. Increasing concentration and cooking time significantiy (P ≤ 0.0001, P = 0.0003, respectively) increased the viscosity of the maize porridges while addition of groundnut, addition of cow's milk and increased shear speed had the desired effect of reducing the viscosity of the porridges (P ≤ 0.0001, P = 0.001, P = 0.0002, respectively). The energy density of the porridges as determined from the proximate values of the raw ingredients showed that refined flour porridges had an average of 4% less energy density than the whole flour porridges at equivalent influencing factors. These results show that refined flour produces porridges of significantly high viscosity (stiff consistence), making it practically impossible for the mothers to increase the energy density of the porridges through addition of more flour. Maize flour for use in weaning porridges should therefore be only moderately refined to avoid the high viscosity/low energy density problems associated with over-refined flours.