Functionality and Appearance of Sorghum‐Pearl Millet Composite Flour Fortified With Oyster Mushroom for Thin Porridges

Abstract

Porridges are the main staple food in sub-Saharan Africa. They are generally starchy and are made from composite flours of various cereals. Evaluation of color, pasting, rheological, and functional properties of the composite flour samples was done, since these influence the cooking and product quality of the porridges. Sorghum-pearl millet blends were substituted at levels from 10% to 50% using oyster mushrooms to form the composite flours. Rheometer and Rapid Visco Analyzer were used in the determination of rheological and pasting properties respectively, while Chroma Meter was used in color determination. Bulk density, water and oil absorption, and swelling qualities were also determined. The study findings indicated that fortified flours had a consistently higher water, oil, and swelling properties indicating that oyster mushrooms have a higher absorption capacity. The color parameters (L* (degree of lightness), b* (yellowness), chroma, hue angle) increased while the pasting parameters (peak, trough, breakdown, final, and setback viscosities) reduced with an increase in oyster mushroom levels; that is, final viscosity decreased with increased oyster mushroom levels in the pearl millet-sorghum flours from 1072.7 ± 61.8 to 216.8 ± 21.2 mPas. For the dynamic rheological tests of the thin porridges prepared from the composite flours showed a distinctive gel-like character under the measurement conditions, an indication that elastic behavior dominated over viscous behavior. The level of storage and loss moduli decreased with increasing substitution levels, which is coherent with the pasting properties. Research on physico-functionality of sorghum-pearl millet composite flours fortified with oyster mushrooms shows that the substitution of mushrooms has no significant negative effect on the composite flour functionality. Oyster mushrooms could therefore be used to fortify cereals without affecting their physical properties.