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To illustrate the correlations between molecular structures and the film-forming properties of thermoplastic starch from various botanical sources, starches from cereal, tuber and legume were modified by thermoplastic extrusion and the corresponding thermoplastic starch films were prepared including thermoplastic corn starch (TCS), thermoplastic rice starch (TRS), thermoplastic sweet potato starch (TSPS), thermoplastic cassava starch (TCAS) and thermoplastic pea starch (TPES) films. TPES film displayed a higher tensile strength (6.28 MPa) and stronger water resistance, such as lower water solubility (15.70 %), water absorption (42.35 %), and water vapor permeability (0.285 g·mm·h -1 ·m -2 ·kPa -1 ) due to higher contents of amylose and B 1 chains. TCAS showed a smoother and more amorphous film due to higher amylopectin content, resulting higher elongation at break and larger opacity. TCS film was the most transparent due to a compacter network and more ordered crystallinity structure, which was suit for the packaging of fresh vegetables and aquatic products, whereas TCAS film was the opaquest, which protected package foods from light such as meat products, etc. The outcome would provide an innovative theory to regulate accurately the functional properties of thermoplastic starch films for different food needs., Competing Interests: Declaration of competing interest We confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome., (Copyright © 2023 Elsevier B.V. All rights reserved.)

To better understand the correlation between structure and properties in thermoplastic starch biopolymer blend films, the effects of amylose content, chain length distribution of amylopectin and molecular orientation of thermoplastic sweet potato starch (TSPS) and thermoplastic pea starch (TPES) on microstructure and functional properties of thermoplastic starch biopolymer blend films were studied. After thermoplastic extrusion, the amylose contents of TSPS and TPES decreased by 16.10 % and 13.13 %, respectively. The proportion of the chains with the degree of polymerization between 9 and 24 of amylopectin in TSPS and TPES increased from 67.61 % to 69.50 %, and from 69.51 % to 71.06 %, respectively. As a result, the degree of crystallinity and molecular orientation of TSPS and TPES films increased as compared to sweet potato starch and pea starch films. The thermoplastic starch biopolymer blend films possessed a more homogeneous and compacter network. The tensile strength and water resistance of thermoplastic starch biopolymer blend films increased significantly, whereas thickness and elongation at break of thermoplastic starch biopolymer blend films decreased significantly. • The structure-function relationship of thermoplastic starch films was analyzed. • Thermoplastic starch films showed higher molecular orientation and crystallinity. • The chains with DP between 9 and 24 and molecular orientation were the dominant factors. • Thermoplastic starch films showed a better tensile strength and water resistance. [ABSTRACT FROM AUTHOR]

In this study, Denghai-685 and Xianyu-335, two major corn cultivars cultivated in East China, underwent hot air drying with different initial moisture contents (20, 25, and 30%) and drying temperatures (60, 90, and 120 °C). The study analyzed the dried corn kernels' starch structure and physicochemical characteristics. Hot-air drying altered the starch shape, transforming it from spherical to polyhedra. This process also reduces the amount of amylose in corn compared to naturally dried samples. Interestingly, higher drying temperatures (90 and 120 °C) increased gelatinization temperature but decreased other gelatinization parameters for both cultivars. The transparency of starch pastes from the two cultivars was improved, but the retrogradation was weakened. The onset, peak, and conclusion temperatures of starches increased as the drying temperature rose, while the gelatinization enthalpy decreased. Hot-air drying increased the relative crystallinity of starches of the two cultivars, peaking at 60 °C. The changes in values of R 1047cm −1 /1022cm −1 and R 995cm −1 /1022cm −1 deduced from infrared spectroscopy suggested that hot-air drying promoted a more ordered crystalline structure of starches from the two cultivars. These findings suggested that the physicochemical and structural characteristics of starches from the two cultivars were significantly influenced by the interaction of initial moisture content and heating temperatures. [Display omitted] • This study aims to better understand the grain drying of two main varieties of corn in East China. • The changes of starch structure and physicochemical properties during drying were studied. • The pasting viscosities of starches from the two corn cultivars differed significantly due to genetic differences. • Hot-air drying reduces the enthalpy change of gelatinization, relative crystallinity and short-range structure of starch. [ABSTRACT FROM AUTHOR]

• Wheat starch was modified with transglucosidase to increase branching degree. • The branching degree increased with increasing transglucosidase treatment time. • Transglucosidase resulted in the reduction in the crystallinity of retrograded starch. • Water mobility of transglucosidase-treated starch increased during retrogradation. • Transglucosidase resulted in the reduction in retrogradation rate constant of starch. To reduce the wheat-flour-based food texture and flavor deterioration caused by starch retrogradation, herein wheat starch, the most ingredient in wheat flour, was modified by transglucosidase to delay long-term retrogradation of wheat starch. The study proposed promising data of transglucosidase-treated starch about structure, crystallinity and retrogradation kinetics. Structural properties showed that transglucosidase treatment shortened the average chain length from 19.49 to 16.10 and induced the dominance of amorphous state. Moreover, branching degree increased from 14.11% to 17.97% after transglucosidase treatment, resulting in higher water mobility. Amylose content increased from 25.33% to 59.00% due to the hydrolysis ability of transglucosidase. Relative crystallinity of the retrograded starches decreased from 24.33% to 14.50%. Furthermore, the Avrami parameters demonstrated that transglucosidase treatment significantly retarded the retrogradation rate of wheat starch due to the decrease of re-crystalline rate. The outcoming would supply a solid theory foundation for exploring the wheat staple foods with higher qualities. [ABSTRACT FROM AUTHOR]

Based on our previous study, or wheat amylose (WA) can supply an appropriate donor for branching enzyme (BE) to generate more new α-1, 6 branch points in waxy rice starch (WRS), sequential glucoamylase (GA) and BE were used to modify the mixtures of WRS and WA in different amylose ratios. The effects of WA on sequential GA and BE catalysis were investigated and the structural and physicochemical properties of the GABE-modified WRS/WA samples were analysed. The results indicated that after GA→BE treatment, the degree of branching significantly increased with increasing ratios of WRS:WA (1:0.2–1:1.2). With increasing ratios of WRS:WA from 1:0.2 to 1:0.8, short chain length distribution (DP 6–12), solubility and loss tangent increased, whereas middle chain length distribution (DP 13–24), relative crystallinity, the rate of starch retrogradation, the gelatinization temperatures and enthalpy values, as well as storage modulus and loss modulus decreased. However, as the ratios of WRS:WA continued to increase (1:1.0–1:1.2), the above results were reversed. These data demonstrated that amylose ratios in WRS:WA mixtures was closely correlated with catalytic efficiency of sequential GA and BE. The outcome would provide a new pathway for controlling amylose ratios in WRS:WA mixtures to obtain the desirable physicochemical properties of waxy rice starch-based products via enzyme modification. Image 1 • Sequential GA and BE modified the WRS:WA mixtures in different amylose ratios. • With increasing ratios of WRS:WA (1:0.2–1:1.2), the branching degree increased. • With increasing ratios of WRS:WA (1:0.2–1:0.8), short chains (DP 6–12) increased. • With increasing ratios of WRS:WA (1:1.0–1:1.2), middle chains (DP 13–24) increased. • Amylose ratios was closely correlated with catalysis of sequential GA and BE. [ABSTRACT FROM AUTHOR]