Structural characterization of casein micelles: shape changes during film formation

Area of Science:

• Food Science
• Materials Science
• Biophysics

Background:

• Casein micelles are complex colloidal particles crucial in dairy products.
• Understanding their structural behavior in films is essential for food processing and material design.

Purpose of the Study:

• To investigate the effect of size-fractionation on the structure of casein micelle films.
• To analyze casein micelle behavior during film formation using advanced scattering techniques.

Main Methods:

• Size-fractionation of casein micelles via centrifugation.
• Dynamic light scattering (DLS) for solution characterization.
• Optical microscopy and Atomic Force Microscopy (AFM) for surface and microstructure analysis.
• Micro-beam grazing incidence small angle X-ray scattering (μGISAXS) for nano- and microstructure determination.

Main Results:

• Size-fractionation yielded casein micelle solutions with narrow, asymmetric size distributions.
• Films exhibited smooth surfaces and homogeneous microstructures.
• μGISAXS revealed larger, broadly distributed sizes in films compared to solution.
• GISAXS patterns indicated casein micelle deformation within the film structure, deviating from spherical models.

Conclusions:

• Centrifugation effectively fractionates casein micelles, influencing their assembly into films.
• Casein micelles undergo significant structural deformation during film formation.
• μGISAXS is a powerful tool for probing the nano- and microstructure of casein films.