Effect of reaction solvents on the multi-scale structure of potato starch during acid treatment

- The mechanism behind solvent effects on acid treatment is explored.
- Acid-ethanol treatment attacks simultaneously on amorphous and crystalline regions.
- Acid-ethanol treatment shows greater extent of disruption on crystalline regions.

Potato starch was treated with 0.36% HCl in ethanol and water for various time periods, and its structural changes were evaluated and compared in this study. Acid-ethanol treated starch (AET-s) had relatively low average molecular weight (Mw) and z-average radius of gyration (Rg), and its solubility was higher than that of the counterpart acid-water treated starch (AWT-s). The granular appearance and differential scanning calorimetry (DSC) profile demonstrated that acid in ethanol and in water exhibited different attack pathways on the granules. No significant difference in crystallinity was observed for AET-s; however, the ratio of absorbance 1022/995 cm−1 and the peak intensity detected by small-angle X-ray scattering (SAXS) were increased with increasing treatment time. These results suggested that ethanol-acid treatment simultaneously attacked on the amorphous and crystalline regions, and the degradation extent on crystalline regions caused by ethanol-acid treatment was higher than that observed by acid-water treatment.

During acid treatment, the reaction solvent had an important effect on the crystalline structural change of potato starch granules. In the granules, the amorphous and crystalline regions were disrupted simultaneously by ethanol-acid treatment, whereas acid in water preferentially attacked the amorphous regions.306