Preparation of weaning porridges from blends of cereals and sweetpotato flours

Abstract

The main objective of this study was to produce a food for infants and children that is nutritious, low in bulk and high in energy content, from blends of cereal and sweetpotato flours. Cured sweetpotatoes from two varieties containing high levels of endogenous amylolytic enzymes and B-carotene were prepared and dried as slices then milled into flour. The flour was blended with maize and millet flours. The effect of curing and subsequent storage of the sweetpotato roots, the effect of drying at temperatures of 50°, 60°, 70° and 80°C, and peeling on the total amylolytic activity and ~- carotene content was determined. The proximate composition of the flour individually and in blends was also determined. The flour blends were used to make porridges which were then analysed for their viscosity and their energy density. It was found that during curing, the roots showed an apparent increase in the total amylolytic activity especially in the first three days. Thereafter, there was a general increase up to the fifth day of subsequent storage at 15°C. It was also observed that drying of the sliced roots at the temperatures of 50°, 60°, 70° and 80°C did not change significantly (P~0.05) the levels of ~- carotene contents and total amylolytic activity. Peeling of the roots also had no significant effect (P~0.05) on their ~-carotene contents and total amylolytic activity. The sweetpotato flours were used to reduce the viscosity and increase the energy density of maize and millet flours of 10,15 and 20% total solids blended in a 1:1 ratio. For a 10% blend, the peak viscosity was increased from 740 Brabender Units (B.U) to 1000 B.U by addition of 36% sweetpotato flour (w/v), and the energy density increased from 175 to 273 kcal/lOOg, a 56% increase. A plain 15% maize-millet blend on the other hand had a viscosity of 1600 B.U and an energy density of 262 kcal/l00g. The viscosity was higher than that of the same concentration, which included sweetpotato flour. The energy density could then be increased with addition of more sweetpotato flour and a reduction in viscosity achieved. Addition of sweetpotato flours up to 60% (w/v) into maize-millet flour blends resulted 111 viscosity reduction as follows: for a 20% blend it was reduced from 2600 B.U to 1970 B.D. A 15% blend showed a reduction of 1590 to 1170 B.U while a 10% blend exhibited a reduction from 760 to 500 B.U. This reduction in viscosity meant that more sweetpotato flour could be added to increase the energy density. Organoleptic tests showed that blending of sweetpotato flours with maize and millet flours enhanced the overall acceptability of the porridge made therefrom over that of the plain maizemillet blend. Substitution of the maize-millet flour blend with sweetpotato flour up to 50% was possible without significantly affecting the acceptability of the final product. The most acceptable final product was made up of a mixture of sweetpotato flour and a blend of maize and millet in a 1:1 ratio. Results showed that porridge with high energy density and high levels of ~-carotene could successively be formulated. The porridge could be used to feed children to meet up to 40% and 110% of the energy and ~-carotene Recommended Daily Allowance, respectively.