Colloidal structures of O/W creams

Area of Science:

• Pharmaceutical Sciences
• Materials Science
• Colloid and Surface Chemistry

Background:

• Oil-in-water (O/W) creams are complex emulsions with diverse applications.
• Understanding their internal structure is crucial for controlling properties like water release.
• Existing models may not fully capture the intricate gel networks within these formulations.

Purpose of the Study:

• To elucidate the colloidal gel structures of O/W creams.
• To investigate the role of water phases within these structures.
• To identify key quality criteria for O/W cream formulations.

Main Methods:

• Small-angle X-ray diffraction (SAXD) for structural analysis.
• Differential scanning calorimetry (DSC) and thermogravimetry (TGA) for thermal properties.
• Freeze fracture transmission electron microscopy (FF-TEM) for ultrastructural visualization.

Main Results:

• O/W creams form two distinct, coherent colloidal gel networks: a hydrophilic and a lipophilic phase.
• The hydrophilic gel phase contains interlamellar water in dynamic equilibrium with bulk water.
• The lipophilic gel phase primarily immobilizes the internal (dispersed) phase, suggesting a four-phase system.
• Thermogravimetry can quantify the ratio of interlamellar to bulk water.

Conclusions:

• The investigated O/W creams are complex four-phase systems.
• The ratio of interlamellarly fixed water to bulk water is a critical quality parameter.
• Controlling this water ratio allows for tailored water release properties of the cream.