Prediction of Shelf Life of Dakuwa (Nigerian cereal/groundnut snack) Using pH as Index of Acceptability

This study was undertaken to establish the effect of pH on the acceptability of dakuwa. Dakuwa was prepared by malting and milling maize grains and groundnut. Maize flour and groundnut paste were mixed together in equal ratios with the addition of sugar and red pepper. pH of fresh dakuwa was varied using citric acid and subjected to sensory evaluation in order to establish the relationship between pH and acceptability of dakuwa. Accelerated storage test was also carried out in order to determine the kinetics of pH change and kinetics of pH change was tested using zero and first order reaction relationships. Linear regression was used to determine Arrhenius equation parameters and the relationship between pH and acceptability. Decreasing pH reduced dakuwa acceptability. Order of pH change was adequately described by both zero and first orders of reaction. From the data generated, using first order reaction kinetics, a relationship was derived which can be used to estimate the shelf life of dakuwa on the basis of pH. Keywords: Dakuwa, pH, acceptability, kinetics, sensory evaluation, accelerated storage, Arrhenius equation, regression, temperature, shelf-lif

Physico-chemical and Sensory Properties of Bread Prepared from Wheat and Orange-Fleshed Sweet Potato (Flour, Starch and Non-Starch Residue Flour) Blends

Bread was produced from wheat (Trititum spp) orange flesh sweet potato (Ipomoea batatas L.) flour, starch and non-starch residue blends. The orange-fleshed sweet potatoes were washed, peeled, sliced, dried and milled to flour. The starch and non-starch residue were also produced from the orange-fleshed sweet potatoes. Different proportions of wheat and flour, wheat and starch and wheat and non-starch residue of orange-fleshed sweet potato with increasing level of orange-fleshed sweet potato at 10, 20, 30 and 40% addition in wheat were prepared. Control samples were 100% wheat flour (A0), 100% orange-fleshed sweet potato flour (A1), 100% orange-fleshed sweet potato starch (B1) and 100% orange-fleshed sweet potato non-starch residue (C1). Breads from these different proportions were formulated. The proximate, mineral, vitamin, physical properties and sensory attributes of the bread samples and their composites were determined. The GENSTAT Statistical Software (version 17.0) was used for data analyses. The Proximate compositions of the bread ranges as follows; moisture 26.30-36.21%, protein 0.85-7.89%, fat 6.33-8.93%, fiber 0.82-4.92%, ash 0.56-2.11% and carbohydrates 41.26-64.84%. The physical properties of the breads ranged from 210.60-254.00 g, 0.05-2.40 mm, 317.60-440.60 cm3 and 1.25-2.10 for loaf weight, oven spring, loaf volume and specific volume respectively. Mineral and vitamin composition for breads samples ranged respectively thus for calcium 18.45-33.21 zinc 0.92-6.27, magnesium 0.28-19.33, phosphorus 31.00-319.60 and potassium 56.30-352.60, vitamin B1, 0.10-0.37, vitamin B2, 0.07-1.23, vitamin B6, 0.09-1.25, vitamin B12 0.04-1.13 mg/100 g, vitamin C 0.12-14.17 mg/100 g and vitamin A 0.00-8193 µg/100 g.The sensory evaluation results indicated that up to 20% substitution of wheat flour with orange-fleshed sweet potato flour, starch and non-starch residue flours was acceptable in bread formulation