Quality characteristics and acceptability of cookies from sweet potato – maize flour blends

Abstract

Purpose – This study aims to assess the quality characteristics and acceptability of cookies from sweet potato–maize flour blends and to determine nutritional quality, color and palatability traits and to compare the effects with that of wheat cookies, so as to suggest a cost-effective production method to bakers and retailers. This would ensure food security, enhanced health, combat malnutrition problems and improve the production of the crops. Design/methodology/approach – Cookies were prepared by the method reported by Okaka and Isieh (1990), Abayomi et al. (2013), Onabanjo and Ighere (2014) with modification. Flour (200 g) from each sample of different flour blends was used for the experiment. Sugar (80 g) was creamed with margarine (100 g) until light and fluffy constituency was obtained using Kenwood chef with initial minimum speed, and the speed increased stepwise until the mark of 6 on the chef indicator was attained. Whole egg (60 g) was added, then followed by flour (200 g), powdered milk (20 g), baking powder (0.1 g) and salt (1 g) were added and mixed until a stiff paste (batter) was obtained. The batter was rolled on a floured board using a rolling pin to a thickness of 0.2-0.3 cm. The rolled batter was cut into circular shapes with a cutter and arranged on a greased tray and baked at 1500°C for 20 minutes. The cookies were brought out, cooked and packaged in cellophane bag until used for laboratory analysis. Findings – The results revealed that substitution of sweet potato flour with maize flour significantly (p < 0.05) reduced the protein from 6.8-4.4 per cent, moisture from 5.3-5.0 per cent, crude fibre from 3.4-2.5 per cent and fat from 9.8-8.5 per cent of the composite flours and the cookies. The ash and sugar contents were increased from 4.3-5.8 per cent for ash and 2.1-3.9 per cent for sugar with increase in sweet potato flour substitution. The calorific value of the cookies decreased from 457-397 cal/100 g as the percentage of sweet potato flour increased in the maize flour cookies. Sensory evaluation results showed that the colour, texture, taste and overall acceptability changed significantly (p < 0.05) with increase in sweet potato flour substitution. The optimum substitution level was 40 per cent; above this, the product becomes less acceptable to the consumer. Research limitations/implications – Fabrication and production processing machines that use sweet potato will be a great challenge. Originality/value – This research is of value to the bakery industry or retailers. The optimum substitution level of sweet potato flour was 40 per cent, and it appears to be a promising measure from the view of practicability. The relative ease of getting sweet potato flour makes it superior to other imported flour like wheat and in reducing cost of importation of wheat to Nigeria.