Measuring interactions between Pickering emulsion droplets coated with casein-chitosan complex using optical tweezers

Area of Science:

• Food science and colloid chemistry
• Interfacial science
• Materials science

Background:

• Protein/polysaccharide complexes are promising for stabilizing emulsions.
• Microscale droplet interactions in these emulsions require further study.
• Understanding Pickering emulsion stabilization mechanisms is crucial.

Purpose of the Study:

• To investigate interaction forces between rice bran oil droplets stabilized by casein-chitosan complexes.
• To correlate interfacial layer properties with emulsion physical stability.
• To explore the impact of pH and ionic strength on emulsion droplet interactions.

Main Methods:

• Optical tweezers were used to measure pN-level interaction forces between emulsion droplets.
• Fluorescence spectroscopy and zeta-potential analysis determined interfacial layer conformation and charge.
• Atomic force microscopy (AFM) and optical microscopy characterized emulsion morphology.

Main Results:

• Force curves correlated well with interfacial layer properties and charge.
• Environmental conditions (pH, ionic strength) significantly affected droplet interactions.
• AFM and optical microscopy revealed structural evolution under varying conditions.

Conclusions:

• Optical tweezers offer a precise method for studying Pickering emulsion droplet interactions.
• Interfacial layer properties are key determinants of emulsion physical stability.
• This research provides insights into the stabilization mechanisms of protein/polysaccharide-stabilized Pickering emulsions.