Abstract
Food processing can modify legume structure and improve its applicability in protein-fortified foods. This study investigated the effects of six pretreatments, including peeling, roasting, atmospheric steaming, high-pressure steaming, sprouting, and microwaving, on the processing characteristics and quality attributes of wheat bread containing 50% red kidney bean flour (RKBF). Results showed that thermal pretreatments reduced the gelatinization enthalpy (ΔH) of composite flours by 4.6–13.2% and increased dough water absorption rate by 5.7–9.7% compared with untreated RKBF. Hydrothermal treatments significantly improved dough rheology and structural integrity by increasing glutenin macropolymer (GMP) content, reducing free sulfhydryl levels, altering protein secondary structure, and optimizing starch and gluten distribution. Atmospheric steaming increased the bread specific volume from 3.37 to 3.53 cm3/g and reduced hardness by 16%. Incorporation of RKBF also reduced rapidly digestible starch from 64.91% in wheat bread to 48.99–56.16% and increased resistant starch from 11.76% to 21.27–25.55%. Moreover, volatile analysis identified 42 compounds, with thermal pretreatments effectively reducing beany flavor compounds. Peeling alleviated dark coloration but further reduced bread volume, whereas sprouting-induced protein degradation adversely affected dough formation and gluten structure. Overall, atmospheric steaming exhibited the best balance between processing performance and nutritional quality, showing a significant improvement in the bread quality containing 50% RKBF.