Development and assessment of frying characteristics, chemical composition, descriptive sensory properties and preference mapping of wheat-orange fleshed sweet potato composite Swahili buns (Maandazi)

Abstract

This study was carried out to investigate frying characteristics, chemical composition and sensory evaluation of whole-wheat buns (WWB) and Wheat-Orange fleshed sweet potatoes - composite buns (WPCB) at different levels of wheat flour substitutions. A whole-wheat buns (WWB) and OFSP-composite buns (WPCB 1, WPCB 2 and WPCB 3) were prepared in triplicate at 0, 10, 20 and 30% levels of wheat flour substitution respectively, and evaluated for weight, volume, specific volume, proximate composition, vitamin A, descriptive sensory profile, consumer liking and preference mapping. Completely randomized design was used to assess and compare frying characteristics, proximate and vitamin A contents between samples with bread types being the principal factor while Randomised complete Block design was used to assess sensory properties and consumer acceptability of the bread samples with panelists and bread types being the principal factors. The results showed that moisture content, crude fibre, and ash contents of the composite buns increased significantly (p<0.05) while the carbohydrate, crude fat and protein contents decreased significantly (p<0.05) with progressive increase in the OFSP flour. The WPCB3 had significantly (p<0.05) highest moisture, ash and fibre values of 17.13, 2.97 and 1.31 g/100g DM, respectively, compared to lowest values of 14.05, 2.17 and 0.48 g/100 g DM, respectively in WWB. However, significantly (p<0.05) higher fat, carbohydrate and protein values of 1.95, 70.68 and 8.06 g/100g DM compared to lowest values of 0.89, 54.13 and 6.56 g/100 g DM, respectively was observed in WPCB 3. Vitamin A content increased significantly (p<0.05) as OFSP flour increased with the highest value of 700 μg/100 g RE DM in WPCB3 and smallest value of 170 μg/100g RE DM in WWB. The mean intensity values of all sensory attributes between samples differed significantly as a wheat flour substitution increased except for taste and aroma between WWB and WPCB 1 which had statistically (p>0.05) similar mean intensity scores in taste, aroma, and texture acceptability as WWB. Similarly, consumers showed statistically similar scores in acceptability between WWB and WPCB 1. The Preference mapping results showed colour and taste were the main drivers for consumer preference. In conclusion, the study shows that the use of OFSP flour up to 10% of the flour into wheat flour produced nutrient enhance buns with similar and acceptable taste, texture, mouth feel and aroma comparable to 100% wheat buns.

Keywords: Chemical composition, sensory evaluation, preference mapping, Orange fleshed sweet potatoes, wheat