Janus-like napins for switchable protein foam stability.

Area of Science:

• Colloid and Surface Science
• Biomaterials Engineering
• Food Science and Technology

Background:

• Protein foams are crucial in food and industrial processes, but their stability is often difficult to control.
• Applications require either highly stable foams (e.g., cappuccino) or easily destabilized foams (e.g., protein extraction).
• Tunable foam stability necessitates precise modulation of interprotein forces.

Purpose of the Study:

• To investigate the tuneability of foam stability using rapeseed proteins (napins) by modulating their electrostatic repulsion.
• To demonstrate how napin's zeta-potential influences interfacial properties and foam behavior.
• To establish a method for controlling protein foam characteristics for diverse applications.

Main Methods:

• Utilized ellipsometry, atomic force microscopy, and interfacial shear rheology to characterize napin interfacial layers.
• Employed thin film balance analyses to determine critical film pressure.
• Varied napin zeta-potential by adjusting environmental pH.

Main Results:

• Napins at 0 mV zeta-potential formed dense, viscoelastic interfacial monolayers, leading to highly stable foams comparable to egg proteins.
• Increasing napin zeta-potential to -15 mV resulted in less dense, liquid-like interfacial layers due to enhanced repulsion.
• Foams destabilized rapidly at -15 mV zeta-potential, with critical film pressure being half that of uncharged napins.

Conclusions:

• The foaming properties of particle-like proteins, such as napins, are highly sensitive to electrostatic repulsion.
• Modulating zeta-potential offers a powerful strategy to tune protein foam stability for specific industrial needs.
• This research unlocks opportunities for leveraging napins in advanced materials and industrial systems requiring controlled foaming.