pH-dependent interactions in OPI/CS composites drive emulsion stability and β-carotene bioaccessibility

Area of Science:

• Food Science
• Biomaterials Science
• Colloid and Surface Science

Background:

• Oat protein isolate (OPI) and chitosan (CS) are biocompatible polymers with potential applications in food stabilization.
• Understanding the interaction between OPI and CS is crucial for optimizing their use in delivery systems.
• Heat treatment of OPI can alter its structure and improve its binding with CS.

Purpose of the Study:

• To fabricate and characterize composite particles of heat-treated oat protein isolate (OPI') and chitosan (CS).
• To investigate the influence of pH and OPI':CS ratio on particle properties and interactions.
• To evaluate the efficacy of OPI'/CS composite particles as stabilizers for beta-carotene emulsions.

Main Methods:

• Fabrication of OPI'/CS composite particles at varying pH and OPI':CS ratios.
• Characterization of particle size, turbidity, and dominant interaction forces (electrostatic vs. hydrophobic).
• Preparation and in vitro digestion of beta-carotene-loaded emulsions stabilized by OPI'/CS particles.
• Assessment of beta-carotene bioaccessibility and retention under different storage conditions.

Main Results:

• Heat treatment of OPI enhanced its binding with CS due to structural unfolding.
• Particle size and turbidity showed a complex response to OPI':CS ratio and pH, indicating shifts in interaction forces.
• Optimal conditions (OPI':CS = 5:1, pH 7) yielded small emulsion droplet size (1.55 μm) with strong hydrophobic interactions.
• The OPI'/CS stabilized emulsion demonstrated high beta-carotene bioaccessibility (36.78%) and excellent storage stability against temperature and UV irradiation.

Conclusions:

• OPI'/CS composite particles are effective stabilizers for beta-carotene emulsions.
• The interaction dynamics between OPI' and CS can be tuned by pH and ratio, influencing emulsion properties.
• These findings highlight the potential of OPI'/CS systems for delivering lipophilic bioactive compounds with enhanced stability and bioavailability.