Confocal microscopy of a dense particle system.

Area of Science:

• Colloid and surface science
• Materials science
• Rheology

Background:

• Understanding particle behavior near interfaces is crucial in various industrial processes, including food manufacturing and materials processing.
• Cornflour starch granules, common in food products, exhibit complex interactions with surfaces.
• Confocal microscopy offers high-resolution imaging for studying microscale phenomena.

Purpose of the Study:

• To investigate the spatial distribution of cornflour starch granules relative to a wall in a paste.
• To develop and apply a 3D particle identification algorithm for analyzing granule positions.
• To examine particle behavior in both static and dynamic (pipe flow) systems.

Main Methods:

• Utilized confocal microscopy with a 40x oil immersion lens to image starch granules (15 µm diameter).
• Employed a solvent matched to the refractive index of granules for imaging up to 120 µm depth.
• Developed a 3D algorithm to accurately identify particle centers and measure number density and velocity.

Main Results:

• Cornflour starch granules were found to be depleted from the wall.
• This depletion zone extended approximately 100 micrometers from the wall.
• The study successfully quantified particle number density and velocity in pipe flow.

Conclusions:

• Starch granule distribution is significantly influenced by proximity to boundaries.
• The developed imaging and analysis techniques are effective for studying particle-wall interactions.
• Findings have implications for controlling texture and stability in starch-based products.