The hydrophobic modification of kappa carrageenan microgel particles for the stabilisation of foams.

Polysaccharides such as kappa carrageenan are often utilised in fat replacement techniques in the food industry. However, the structural role they can provide within a product is limited by their hydrophilic nature. Hydrophilic particles can be surface-activated by hydrophobic modification e.g. in-situ interaction with a surfactant. This can drastically improve foam stability by providing a structural barrier around bubble interfaces offering protection against disproportionation and coalescence. Hence, it should be possible to bind negatively charged kappa carrageenan particles with a cationic surfactant through electrostatic interaction, in order to alter their surface properties. Lauric arginate was mixed with kappa carrageenan microgel particles at various concentrations and the potential electrostatic interaction was studied using zeta potential, turbidity and rheological measurements. Mixtures were then aerated and foaming properties explored, in particular the location of the particles. Lauric arginate was successfully bound to kappa carrageenan microgel particles. Consequently, particles were surface-activated and adsorbed at the air/water interface, as shown by optical and confocal microscopy. Foam half-life peaked at an intermediate surfactant concentration, where there was sufficient surfactant to coat particle surfaces but the concentration was low enough to prevent the formation of large aggregates unable to adsorb at the a/w interfaces.