Contribution of selected ingredients to the quality of wheat/unpeeled orange fleshed sweet potato puree composite bread

Abstract

The development of bread from composite formulations is increasing and has attracted much attention from researchers driven by the desire to find non-wheat-bread-making alternatives in order to reduce dependence on imported wheat. However, formulation and production of acceptable composite bread requires understanding the effects of ingredients on bread quality. this study aimed at assessing the contribution of selected ingredients to the quality of composite dough made from wheat flour and unpeeled orange-fleshed sweet potato (OFSP) puree as well as physical qualities, nutritional composition, and consumer acceptability of the resultant bread. A 2-level fractional factorial design (28-3) at resolution IV was used to design a screening experiment and Response Surface Methodology (RSM) was used to analyze data. Prmax and water Absorption of the composite dough were studied using the alveoconsistograph. Physical properties and nutritional composition of composite bread were analyzed using AACC, AOAC and ICC standard methods. Consumer acceptability was assessed by an untrained panel of evaluators using a 9-point Hedonic scale. Significant models were developed at p<0.05 and coefficient of determination, R2 was used to test fitness of the model terms. Prmax and Water absorption decreased as proportions of unpeeled OFSP puree increased from 20% to 50%. Proportion of unpeeled OFSP puree negatively affected crumb colour, specific volume, springiness, flavour, aroma and general acceptability but had a positive effect on weight, moisture content, Total carotenoid content, β-carotene content, vitamin A content, reducing sugar content, protein content, Amylose and amylopectin ratio and starch content. Yeast positively affected volume and crust colour with negative effect on baking loss, staling rate, firmness and chewiness. Treatment of unpeeled OFSP (pasteurized and unpasteurized/fresh) negatively affected texture. Variety had a significant effect on crude fiber with NASPOT13O having a negative effect and NKB135 exhibiting a positive effect. Fat negatively affected cohesiveness. Ascorbic acid (improver) had the least effect on the study responses. Principal component Analysis indicated a negative correlation between nutritional and sensory properties. a positive correlation between textural properties and sensory properties and a high correlation between physical and sensory properties of the bread were observed. The study concluded that the most significant among the selected ingredients that affected quality of wheat/unpeeled OFSP puree bread were proportion of puree, yeast and fat. The study also concluded that treatment and variety had significant effects on the quality of the composite bread.