Abstract:
Child malnutrition remains a major public health problem in low-income African communities, caused by factors including the porridge rheology, poor oral texture quality and low nutritional value of mainly the indigenous/local complementary porridges (CPs), but also some commercially available complementary porridges (CACFs) fed to infants and young children. The flow properties (viscosity) of common indigenous/locally available African CPs (n = 8) plus CACFs (n = 23) were investigated at shear rates 0.001/s – 1000/s and 40 °C, using a rotational rheometer. The perception of the oral texture of the selected African CPs, Maize, Sorghum, Cassava, Orange-fleshed sweet potato (OFSP), Cowpea, and Bambara) and CACFs was investigated by a trained temporal-check-all-that-apply (TCATA) panel (n = 10). A simulated OP method (Up-Down mouth movements- munching) and a control method (lateral mouth movements- normal adult-like rotary chewing) were used. Energy densities of the flour were calculated from proximate analysis data using Atwater factors, and the solids (%) at which the porridge samples had viscosity of 3 Pa.s used to determine the porridges’ energy and protein densities. Results showed a first-order exponential relationship between the apparent viscosity and solids (%) at all shear rates. Maize, sorghum and cassava porridges had very high viscosity profiles and consistency coefficients- K values (173.2; 134.7 and 105.9 Pa.sn respectively) compared to a reference sample (4.7 Pa.sn) and OFSP (3.5 Pa.sn). The Cross model was able to predict the zer-shear viscosity of CPs, with maize, sorghum, cassava porridges (10 % solids), as well as some CACFs having very high zero-shear viscosity values. Some commercially available complementary foods (CACFs) also had high viscosity values and did not meet the WHO and Codex standards for energy and protein content. TCATA results showed that Maize,
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Cassava, and Sorghum porridges, and some CACFs were too thick, sticky, slimy, and pasty, and at the end not easy to swallow even at low solids content—especially by the Up-Down method, which simulates food oral processing in infants. Unsuitable oral texture limits nutrient intake in infants given their limited OP abilities, leading to protein-energy malnutrition. At very low shear rates estimates for infant oral processing, all indigenous complementary porridges, and some CACFs did not provide adequate energy to infants and young children (6 – 24 months), compared to OFSP. Further work is required to improve the viscosity and sensory properties of both African indigenous porridges and CACFs for optimization of infant nutrient intake. There is need to establish more precise shear rates applicable for in-mouth oral processing in infants and young children to assist in the design of infant foods of suitable oral texture.
