Diffusing wave spectroscopy study of the colloidal interactions occurring between casein micelles and emulsion...

Area of Science:

• Colloid and Surface Science
• Food Physics
• Biophysical Chemistry

Background:

• Understanding interparticle forces in colloidal systems is crucial for predicting bulk properties.
• Casein micelles and protein-stabilized fat globules are key components in dairy systems.
• Predicting colloidal behavior requires accurate models of particle interactions.

Purpose of the Study:

• To investigate the colloidal behavior of casein micelles and protein-stabilized fat globules.
• To compare experimental data with theoretical hard-sphere models.
• To identify factors influencing deviations from theoretical predictions.

Main Methods:

• Transmission diffusing wave spectroscopy was used to observe colloidal interactions.
• Turbidity parameter (l*) and diffusion coefficients were measured experimentally.
• Experimental results were compared to theoretical calculations for hard-sphere systems.

Main Results:

• Casein micelles and whey protein isolate (WPI)-stabilized emulsions showed no deviation from the hard-sphere model.
• Sodium caseinate (NaCas)-stabilized emulsions in milk permeate resembled the hard-sphere model.
• NaCas-stabilized emulsions in low ionic strength buffer deviated due to enhanced steric stabilization.
• Mixtures of casein micelles and protein-stabilized droplets showed significant deviation from the hard-sphere model.

Conclusions:

• The hard-sphere model effectively describes casein micelle and WPI-stabilized emulsion behavior under typical conditions.
• Low ionic strength environments enhance steric stabilization in NaCas-stabilized emulsions, causing deviations.
• Mixing different colloidal species introduces complexities not captured by simple hard-sphere models.
• These findings are vital for controlling the stability and properties of dairy-based colloidal systems.