Jamming to unjamming: Phase transition in cyclodextrin-based emulsions mediated by sodium casein

Area of Science:

• Colloid and Surface Science
• Food Science and Technology
• Materials Science

Background:

• Cyclodextrin (CD) self-assembles into solid particle membranes via CD-oil inclusion complexes (ICs).
• Sodium casein (SC) can adsorb at interfaces, potentially altering interfacial film properties.
• High-pressure homogenization can enhance component interactions, promoting interfacial film phase transitions.

Purpose of the Study:

• To investigate how sequential and simultaneous addition of SC influences the assembly and phase transitions of CD-based interfacial films.
• To determine the impact of these phase transitions on emulsion flocculation and stability.
• To characterize the physicochemical properties of emulsions and films using advanced rheological techniques.

Main Methods:

• Sequential and simultaneous addition of SC to CD-based systems.
• Analysis of interfacial film phase transitions using interfacial and large amplitude oscillatory shear (LAOS) rheology.
• Characterization of emulsion and film properties including structural arrest, interfacial tension, interfacial rheology, linear rheology, and nonlinear viscoelasticities via Fourier transform (FT)-rheology and Lissajous-Bowditch plots.

Main Results:

• Interfacial and LAOS rheology revealed a transition from jammed to unjammed interfacial films.
• Two types of unjammed films were identified: SC-dominated liquid-like films (fragile, promoting coalescence) and cohesive SC-CD films (aiding rearrangement, retarding flocculation).
• The cohesive SC-CD film structure was crucial for enhancing emulsion stability.

Conclusions:

• Mediating the phase transformation of interfacial films by controlling SC addition is a viable strategy to improve emulsion stability.
• The formation of cohesive SC-CD films effectively hinders droplet flocculation.
• Understanding interfacial film dynamics is key to designing stable emulsions.