Structural features and thermal property of propionylated starches with different amylose/amylopectin ratio

- Hydrophobic propionylated starches were prepared with different amylose content.
- Crystalline regions were destroyed and also involved in acylation reaction.
- Amylose formed ordered structure within propionylated starch granules.
- Propionylated starch containing more amylose was thermally enhanced more greatly.

This work concerned the effects of amylose/amylopectin ratio on the structure and thermal stability of propionylated starches with high degree of substitution (DS). Four starches with different amylose content were used to obtain propionylated starches. Acylation partly disrupted granule morphology of native starches, and the imperfection and porous structures of starch granule were intensified along with the increased amylose content. It was noted that the crystalline structure of starch was destroyed and thus intense acylation occurred in both amorphous and crystalline regions. The acylated starch with high-amylose content displayed more ordered region compared to low-amylose starch. Acylation enhanced the thermal stability of starch, and this effect became more evident as the amylose content increased. Thus, the amylose/amylopectin ratio has been confirmed capable of affecting the structure and thermal behaviors of hydrophobic propionylated starch, which is of value for the design of starchy materials with tailored thermal stability.