Effect of yam flour substitution on physicochemical and sensory characteristics of wheat flour bread

Fresh yams are perishable goods. However, when dried and milled into flour, yam becomes a durable commodity that can be stored for several months. Thus, the niche of yam flour-included products should be explored. This study aimed to investigate the effect of yam flour substitution on the proximate composition, physical, and sensory characteristics of wheat bread loaves. Yam (Dioscorea rotundata) flour (YF) was obtained and mixed with wheat flour (WF) at substitution levels of 0 (i.e., 100% WF, control), 15, 25, 35, and 50% for bread production. The results were subjected to analysis of variance (ANOVA) followed by Tukey's test (p ≤ 0.05). The proximate composition of the bread samples ranged from 24.73% to 28.04% moisture, 1.48 % to 3.53% fat, 5.63% to 9.39% protein, 1.34% to 1.92% ash, and 60.89% to 62.29% carbohydrate. YF incorporation reduced the loaf’s specific volume (3.25, 2.89, 2.80, 2.78, and 2.74 mL/g) and increased the crumb firmness (4.80, 7.79, 7.99, 8.64, 13.56 N/s). Water activity had no significant difference. There was no surface cracking in loaves with 0, 15, and 25% yam flour substitution, while higher YF substitution led to small cracks. Panelists found no statistical difference between the acceptability (i.e., 7.42 out of 9) of 0, 15, and 25% YF loaves. Higher YF substitution loaves received significantly lower acceptability scores (i.e., 6.33 for 35% YF and 6.07 for 50% YF). In conclusion, this study showed that substitution of YF in bread making is feasible, and up to 25% YF could be included in a bread formulation without impact to the sensory acceptance of the bread.