Mechanism of reduced steamed bun hardness via the addition of single helical corn amylopectin

Abstract The elderly population has been found to prefer softer steamed buns, as they often find regular steamed buns too firm. In this study, the hardness of the steamed bun was reduced by 75.0%, from 2318.7 to 579.6 g, through the addition of 5% single-helical corn amylopectin (SHCAP). SHCAP was characterized by the methylene stretching vibration at 2920 cm−1 and the C–O stretching vibration at 1020 cm−1. The composition of the sample was found to contain a higher proportion of chains with 5–30 glucose residues. The formation of hydrogen bonds between the hydroxyl groups at C1 of SHCAP, water molecules, and protein amide bonds in steamed buns has been observed, resulting in a decrease in the β-sheet structure of proteins in steamed buns. This alternative structure has been demonstrated to enhance water retention, thereby mitigating the hardness of steamed buns. The presence of a diffraction angle at 2θ 16.86° (d=0.526 nm) has been identified as an indicator for softer steamed buns. The findings presented in this study underscore the potential of NaCl-co-crystallized SHCAP as a novel natural additive for improving the texture of starch-based foods.