Electron Microscopy
Electron microscopy utilizes electrons instead of light to meticulously examine the structural characteristics of functional starch granules. Techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) offer unique insights into the microstructural changes in starch granules after various treatments. SEM provides quasi-three-dimensional surface topography, while TEM is ideal for characterizing morphology, crystalline structure, and elemental information. AFM, operating at constant settings, analyzes granule topography on micro or nanoscales.
Differential Scanning Calorimetry (DSC)
DSC, a thermoanalytical technique, evaluates heat flow differences between a sample and an inert reference during programmed temperature changes. Power compensation DSC is commonly used for functional starch analyses, determining key parameters such as gelatinization, retrogradation, glass transition, and starch-lipid complexation.
X-Ray Powder Diffraction (XRD)
XRD unveils the atomic and molecular structure of crystalline and semicrystalline samples, helping classify starches into A-type, B-type, and C-type polymorphs. This technique is crucial for understanding crystalline polymorphic structures during preparation and processing stages.
Nuclear Magnetic Resonance (NMR) Imaging
NMR imaging, based on resonance phenomena, provides valuable insights into starch chemical composition, molecular order, branching, and interactions. Techniques like 1H-NMR efficiently determine branching and amylose content, while solid-state 13C CP/MAS NMR analyzes granular starch molecular order and V-type inclusion complexes.
Rheometry
Rheometry, employing rotational and shear methods, explores the flow behavior of starch suspensions. Dynamic rheometry assesses dynamic conditions, offering information on energy storage, dissipation, and gel structure changes during temperature variations.
Size Exclusion Chromatography (SEC)
SEC, also known as gel filtration chromatography (GFC) or gel permeation chromatography (GPC), stands out as a crucial technique for molecular size characterization of starches. Employing dissolution, separation, detection, and data processing steps, SEC provides insights into the molecular structure of functional starch molecules.
These comprehensive techniques collectively offer a thorough understanding of the structural, thermal, and rheological aspects of functional starches, facilitating advancements in starch characterization for diverse applications.