Improving the Quality of Composite Bread Using Amylolytic Hydrolyzed Orange Sweet Potato Flour and Hydroxypropyl Methylcellulose

The incorporation of non-wheat flours to a composite bread formula presents a significant challenge in its development.This study aimed to improve bread quality particularly in terms of loaf volume, crumb structure, moisture retention, and dough machinability by substituting wheat flour with orange sweet potato flour hydrolyzed using amylase produced by Bacillus spizizenii ATCC 6633 and adding hydrocolloid hydroxypropyl methylcellulose (HPMC).Fifteen bread formulations containing hydrolyzed orange sweet potato flour (HOSPF; 0-60 g/100 g flour blend) and HPMC (0-3 g/100 g flour blend) were evaluated.Amylolytic hydrolysis significantly modified the physicochemical properties of orange sweet potato flour, as indicated by enhanced hydration gel properties, altered pasting behavior, disrupted starch microstructure, as well as increased reducing sugar content, amylopectin-to-amylose ratio, and β-carotene retention.Incorporation of HOSPF increased crumb firmness and color intensity.The effect of HPMC on loaf volume, specific volume, and dough machinability depended on HOSPF level in the formula.Among all formulations, A1H0 (15 g HOSPF/100 g flour blend), A1H2 (15 g HOSPF/100 g flour blend + 3 g HPMC/100 g flour blend), and A2H0 (30 g HOSPF/100 g flour blend) exhibited the most balanced characteristics.These results demonstrate that the combined use of amylolytic hydrolysis and HPMC offers an effective strategy to enhance the composite bread quality.