Multi-scale structure and digestive property of bran starch in different particle size wheat bran

In this study, the multi-scale (granular, molecular, crystalline, lamellar and helical) structure and digestive property of starch isolated from wheat bran of different particle size, including plant scale (1110 μm), tissue scale (235 μm, 83 μm) and cell scale (19 μm), were investigated and compared with wheat flour starch. Bran milling modified bran starch to varying degrees. Tissue-scale milling of bran reduced the granule size of bran starch, but did not significantly modify its molecular, lamellar, crystalline and helical structure. However, cell-scale milling caused significant destruction of crystalline regions and double helix, and increase in starch digestibility. In addition, compared to wheat flour starch, wheat bran starch had more resistant starch and lower digestibility, which were highly correlated with its thinner lamellas, more double helix proportion and compact fractal. This study highlights the effect of supramolecular structure on bran starch digestibility and contributes to the application of bran starch.