Interplay between bulk aggregates, surface properties and foam stability of nonionic surfactants

Area of Science:

• Food science and technology
• Colloid and surface science
• Materials science

Background:

• Previous research demonstrated foam stability exceeding 10 days using specific nonionic surfactants at high sugar concentrations.
• Understanding the relationship between surfactant molecular structure and foam stability is crucial for developing stable food and pharmaceutical foams.

Purpose of the Study:

• To investigate the interrelation between surfactant structure and foam stability.
• To explore the impact of varying hydrophobic chain lengths and hydrophilic head groups on foam performance.
• To identify key structural features that promote exceptional foam stability.

Main Methods:

• Investigated 6 polyoxyethelene alkyl ethers and 12 fatty acid esters with diverse hydrophobic chains (C12, C16, C18, C18:1) and hydrophilic head groups (sorbitol, glycerol, sucrose).
• Assessed foam stability at room temperature over extended periods.
• Analyzed the role of aqueous phase gelation and adsorption layer properties.

Main Results:

• Sucrose palmitate and stearate yielded foams stable for over 100 days.
• Foam stability decreased with increased ethoxy (EO) groups, shorter surfactant tails, and the presence of double bonds in the tail.
• Diesters present as admixtures enhanced foam stabilization by improving adsorption layer packing.

Conclusions:

• Exceptional foam stability is achieved through aqueous phase gelation and the formation of solid-like adsorption layers that prevent drainage and slow Ostwald ripening.
• Surfactant molecular architecture, including tail length, head group, and purity (absence of diesters), significantly influences foam stability.
• Findings provide a predictive tool for selecting surfactants for food and pharmaceutical foam applications.