Physicochemical and nutritional properties of Chinese steamed bread fortified with red beetroot powder and their changes during the making process

Abstract

Chinese steamed bread (CSB) is gaining popularity throughout the world, as it is easy to prepare, economical, and convenient. However, wheat flour based CSB is deficient in essential nutrients. The purpose of the present study was to investigate the potential of red beetroot powder (RBP) as a component in CSB manufacturing to improve its nutritional status. Different proportions of RBP were added into CSB with 0%, 10%, 30%, 50%, and 70% substitutions. The physicochemical, nutritional, and functional properties of the flour mixtures and resulting CSB were investigated. The results showed that the RBP was rich in fibre and minerals. According to the rheological results, the addition of RBP into the wheat flour mixture confers a weakening effect regarding the stability of the dough. The study also revealed that CSB fortified with RBP displayed lower water activity compared to the control sample, which was reflected in the microbiological examination. The addition of RBP prolonged the shelf-life of CSB during storage. Increasing the level of incorporation of RBP decreased lightness, volume, staling rate, and the expected postprandial glycaemic responses of CSBs. Simultaneously, there was an increase in hardness, chewiness, total phenolic content (TPC), antioxidant activity, and betanin content. The substituted CSBs with 10% RBP gave the best sensory profiles in terms of similarity to the negative control sample. This research also investigated the effect of CSB-making processes on the microstructure, TPC, antioxidant activity, betanin content, and thermal properties of CSB. Steaming had a significantly positive impact on TPC and antioxidant activity, while the betanin content and the enthalpy of gelatinisation declined after steaming. It was concluded that an acceptable CSB can be produced by substituting 10% RBP without adversely affecting quality. This particular level can be recommended for delivering a staple food with an enhanced nutritional profile and eating quality.