Encapsulation Using Plant Proteins: Thermodynamics and Kinetics of Wetting for Simple Zein Coacervates

Area of Science:

• Biopolymer science
• Food science
• Materials science

Background:

• Complex coacervates of oppositely charged biopolymers are traditionally used for encapsulating oil-soluble payloads.
• Proteins, like zein, can form simple coacervates independently under specific conditions.
• Exploring plant-based encapsulation systems using simple protein coacervates is an emerging area.

Purpose of the Study:

• To investigate the potential of simple zein coacervates for plant-based encapsulation of oil droplets.
• To understand the physical properties of zein coacervates and their limitations in encapsulation.
• To identify optimal conditions for forming stable capsules using zein coacervates.

Main Methods:

• Zein protein was used to form simple coacervates in mixed water/propylene glycol (PG) solvents.
• Encapsulation of limonene oil droplets was attempted under varying conditions.
• Physical properties of zein coacervates, including interfacial tension and charge, were analyzed.
• pH-dependent kinetics of coacervate droplet deposition and interactions were studied.

Main Results:

• Zein coacervates can encapsulate limonene droplets, but only under specific conditions.
• Simple zein coacervates exhibit significant net charge, unlike charge-balanced complex coacervates.
• Zein coacervates show thermodynamically favorable spreading at oil droplet interfaces due to low interfacial tensions.
• Coacervate capsule formation is highly pH-dependent, with a sharp optimum around pH 8.

Conclusions:

• Simple zein coacervates offer a potential route for plant-based oil droplet encapsulation.
• The unique physical properties of zein coacervates, particularly their charge and pH-dependent kinetics, dictate encapsulation efficiency.
• Precise control over pH is crucial for achieving optimal capsule formation with zein coacervates.