Abstract
Heat-moisture treatment (HMT) changed the morphology and the degree of molecular ordering in lotus rhizome (Nelumbo nucifera Gaertn.) starch granules slightly, leading to some detectable cavities or holes near hilum, weaker birefringence and granule agglomeration, accompanied with modified XRD pattern from C- to A-type starch and lower relative crystallinity, particularly for high moisture HMT modification. In contrast, annealing (ANN) showed less impact on granule morphology, XRD pattern and relative crystallinity. All hydrothermal treatment decreased the resistant starch (from about 27.7–35.4% to 2.7–20%), increased the damage starch (from about 0.5–1.6% to 2.4–23.6%) and modified the functional and pasting properties of lotus rhizome starch pronouncedly. An increase in gelatinization temperature but a decrease in transition enthalpy occurred after hydrothermal modification, particularly for hydrothermal modification involved with HMT. HMT-modified starch also showed higher pasting temperature, less pronounced peak viscosity, leading to less significant thixotropic behavior and retrogradation during pasting-gelation process. However, single ANN treatment imparts a higher tendency of retrogradation as compared to native starch. For dual hydrothermally modified samples, the functional properties generally resembled to the behavior of single HMT-modified samples, indicating the pre- or post-ANN modification had less impact on the properties HMT modified lotus rhizome starch.
Highlights
IntroductionStarch is a semi-crystalline biopolymer that serves as a storage carbohydrate for energy reserves in many plants, including cereals, roots, tubers, seeds, and fruits
Starch granules in storage tissues can vary in shape, size, amylose/amylopectin ratio and functional properties [1]
The objective of this study is to investigate the impact ing, and dual hydrothermal modifications on the granule morphology, resistant starch of heat-moisture treatment, annealing, and dual hydrothermal modifications on the granule content and functional properties of starches isolated from two common varieties of lotus morphology, resistant starch content and functional properties of starches isolated from two rhizome harvested in Taiwan, namely Tsai-ou and Shih-lian
Summary
Starch is a semi-crystalline biopolymer that serves as a storage carbohydrate for energy reserves in many plants, including cereals, roots, tubers, seeds, and fruits. Starch granules in storage tissues can vary in shape, size, amylose/amylopectin ratio and functional properties [1]. Application of native starches in the food industry is kind of limited due to their relatively poor thermal, shear, and acid stability, and the high rate and extent of retrogradation during storage [2]. These disadvantages can be improved by different kinds of modification methods, including physical, chemical and enzymatic methods [3]. The physical modification of starch by moisture, heat, shear, or radiation has been gaining attention due to the fact that no residues of chemical reagents are present in the modified starch, and can be considered as more natural with higher safety
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