Potato starch granule nanostructure studied by high resolution non-contact AFM

Area of Science:

• Food Science
• Materials Science
• Microscopy

Background:

• Starch granules are complex semicrystalline polymers central to food and industrial applications.
• Understanding starch granule nanostructure is crucial for optimizing its properties.
• Previous models proposed granular structures, but direct nanoscale visualization was limited.

Purpose of the Study:

• To investigate the nanostructure of potato starch granules under ambient conditions after freeze-thaw cycles.
• To analyze the surface morphology and internal lamellar organization of starch granules.
• To correlate observed nanostructures with existing models of starch granule architecture.

Main Methods:

• High-resolution non-contact atomic force microscopy (nc-AFM) was employed for surface studies.
• Potato starch granules were subjected to multiple freezing and thawing cycles.
• Analysis included surface topography and estimation of internal lamellar distances.

Main Results:

• Freeze-thaw treatment induced separation and chain-like organization of surface elements.
• Oblong nodules (20-50 nm) were observed on the surface, also found in ethanol precipitates and on other starch types.
• Eroded surfaces revealed internal lamellar structures with 30-40 nm inter-lamellar distances.

Conclusions:

• The observed nanostructures, including surface nodules and lamellar organization, align with the blocklet model of starch granules.
• The findings suggest that surface sub-particles correspond to amylopectin side chain clusters forming blocklets.
• nc-AFM provides high-resolution insights into starch granule nanostructure and the impact of physical treatments.