Effect of Rolling Treatment on Quality of Acetylated Starch and Its Mechanism

To investigate the effect and mechanism of rolling treatment on quality of acetylated starch, the different rolling treatment time (0, 2, 5, 7, 18 h) on acetylated sweet potato starch quality, structures and physicochemical properties of acetylated starch were studied with sweet potato starch as raw material. The mechanism of rolling on the quality of acetylated starch was analyzed according to the related theories of mechanochemistry. The results indicated that, after rolling for 2 h and 7 h, the reaction efficiency increased to 74.45% (2 h) and 75.40% (7 h) respectively, and other qualities (solubility, swelling power and peak viscosity) of acetylated starch increased prominently. After 2 h of rolling processing, compared with native starch, the crystallinity reduced and the diffraction peak at 17.8° level disappeared, the T₂ value increased, gelatinization enthalpy and peak viscosity decreased, and thermal stability weakened. After 5 h of rolling processing, the solubility, swelling power and peak viscosity were all declined, while the thermal stability of starch increased. Compared with that of 2 h of rolling handling, the crystallinity with 5 h treatment increased, value of T_{2, 2} disappeared. After 7~18 h of rolling processing, the crystallinity, gelatinization enthalpy and thermal stability significantly declined, while the value of T_{2, 1} increased. After rolling treatment for 18 h, the double helix structure in crystalline region was arranged in a short-range orderly manner. These changes indicated that rolling had a significant mechanochemistry effect on sweet potato starch granules. With the increase of rolling time, the interior of starch granules gradually experienced the stress, aggregation and agglomeration stages consecutively. Three stages of mechanochemistry effect of starch varied in terms of influence mechanisms, which laid a theoretical foundation for the advanced equipment of preparing high performance modified starch in the future.