The effect of dual modifications of pullulanase debranch and propionylation on rice starch property was investigated in this study. The occurrence of the propionylation in starch molecules was confirmed due to the formation of a new peak at 1750 cm −1 in FTIR spectrum and the characteristic peaks around 1.0 (methyl) and 2.2 (methylene) ppm in NMR compared with the native starch. Interestingly, because of the higher tendency of molecular retrogradation following the debranching, the current results revealed that there was no positive correlation between the amylose content (AC) and the debranching time. Debranching treatment increased the degree of substitute (DS) of the propionyl starch, and the AC was positively correlated with DS (R = 0.7753*), indicating that AC is an important element affecting propionyl reaction due to the exposure of more available hydroxyl groups during debranching. Meanwhile, debranching led to an increased crystallinity level and the crystallinity pattern changed from A-type to B-type, which is associated with the changes in their corresponding hydrolysis resistance. The NMR data also proved that the propionylation involves the replacements of the glucose in the starch structure (C-2, C-3 and C-6) with acyl groups of the desired complexes. Furthermore, the sequence of the reactions that occur in the process of propionylation and their mechanisms are proposed in the current study.
The structures of starch and starch-based materials determine additives migration from material matrix. Propionylated starch derived from waxy, normal, G50 and G80 starch were selected as the matrix, the amylose effect on plasticizer (triacetin) migration as well as structural changes in hydrophobic starch-based films were discussed. The constant ( k 1 ) of first-order rate and initial release rate ( V 0 ) of triacetin migration were consistent with the increment of amylose content. Meanwhile, diffusion model disclosed that Fick's second law was apposite to characterize the short-term migration of triacetin, and larger diffusion coefficient ( D ) values of short- and long-term migration were also found in films with higher amylose content, indicating that amylose-formed structures were in favor of triacetin migration. In comparison of propionylated amylopectin , Van der Waals's interactions between propionylated amylose and triacetin were easier to be weakened with the migration of triacetin, which promoted the decrease of wavenumber of C-O-C, and enlarged the inter-planner spacing of crystalline structures, promoting the formation of amorphous structures and wrinkles and embossments in films with higher amylose content. This work confirmed that regulating the structures of starch were effective to control the migration behavior of additives from starch-based films.
危险品化学品经营许可证（带存储）