Physicochemical, structural and nutritional properties of steamed bread fortified with red beetroot powder and their changes during breadmaking process

Beetroot (Beta vulgaris) is a source of diverse nutrients such as dietary fibers and betalains. Chinese steamed bread (CSB) has gained popularity in recent years. Red beetroot powder (RBP) was added (up to 70%) in wheat flour to make nutritionally fortified CSB. RBP addition greatly decreased specific volume (1.39 to 0.53 mL/g) and staling rate (4.14 to 2.59%), while increasing hardness (2882 to 15056 g) and chewiness (1923 to 3174 g) since RBP affected gluten secondary structure and weakened dough strength. More importantly, CSB containing RBP exhibited improved in vitro antioxidant potential and reduced estimated glycemic index (70.8 to 60.7). The betalains were largely degraded during steaming due to the isomerization of betanin to isobetanin. Sensory analysis showed that wheat flour could be substituted by RBP up to 10% without compromising the eating quality of the CSB. The findings indicated the feasibility of formulating beetroot-fortified foods with enhanced nutritional quality.