Effects of adding food ingredients rich in dietary fiber and polyphenols on the microstructure, texture, starch digestibility and functional properties of Chinese steamed bun

This study incorporated pitaya (dragon fruit), kudzu root, and Hericium erinaceus (DKH) as functional ingredients into Chinese steamed bun (CSB) to investigate their impact on nutritional composition, textural properties, microstructure, starch digestibility, and postprandial glycemic response. The optimal DKH incorporation ratio was determined using single-factor and response surface methodology experiments. Compared to traditional CSB, DKH enrichment significantly increased dietary fiber and phenolic content. However, DKH incorporation significantly affected textural properties, resulting in increased hardness and reduced elasticity and cohesiveness relative to wheat flour CSB. Microstructural analysis revealed that DKH disrupted the gluten network structure. DKH fortification significantly decreased in vitro starch digestibility and the estimated glycemic index (EGI), with the starch hydrolysis rate decreasing by 19.2 % and EGI decreasing from 94.6 ± 1.3 to 80.3 ± 0.8. Additionally, DKH-CSB showed enhanced antioxidant capacity and favorable modulation of gut microbiota, demonstrating its potential as a functional low-glycemic-index food. • The incorporation of DKH increased the dietary fiber content of CSB. • The dietary fiber in DKH disrupts the gluten network structure. • Starch digestibility in CSB is lower after DKH incorporation. • DKH incorporation reduces the hydrolysis index and glycaemic index of CSB. • The DKH-CSB causes less postprandial blood glucose fluctuations.