Kafirin-based Pickering stabilizers: Tailoring interfacial properties with gum Arabic

Kafirin, a major prolamin of sorghum with high homology to the well-studied zein, has shown the potential to be a Pickering stabilizer by self-assembling into nanoparticles, but its behavior at oil-water interfaces is still largely unknown. Kafirin nanoparticles (KNPs) generally have high surface hydrophobicity, which will largely influence their interfacial properties. This study aims to understand and tune the oil-water interfacial properties of KNPs by adjusting their surface hydrophobicity with gum Arabic (GA). We measured the adsorption behavior of KNPs and kafirin-GA nanoparticles (KGANPs) and their linear and nonlinear interfacial dilatational rheological behavior, where we used the general stress decomposition (GSD) method to quantify the nonlinear behavior. This study found that KGANPs had relatively larger particle sizes, higher values of zeta potential, and better dispersibilities than KNPs. KGANPs adsorbed slower at oil-water interfaces, but produced stiffer interfaces. The presence of GA influences particle interactions at interfaces, leading to a significantly altered nonlinear rheological behavior: KGANPs interfaces derive their strength more from resistance against density changes compared to plain KNPs interfaces. In emulsification tests, the Pickering emulsion stabilized by KGANPs 1:1 (with a kafirin-to-GA mass ratio of 1:1) demonstrated better flow and storage stabilities compared to KNPs-stabilized emulsion. These findings provide insights into the behavior of kafirin-based nanoparticles at oil-water interfaces and in emulsion stabilization, and show the potential of gum Arabic in tuning their oil-water interfacial behavior for developing novel Pickering emulsion-based products in food, pharmaceuticals, and cosmetics. • The wettability of kafirin (K) nanoparticles can be tuned with gum Arabic (GA). • K-GA nanoparticles formed stiffer O/W interfaces than kafirin nanoparticles. • GA has a strong effect on the interactions between particles at O/W interfaces. • GA increased the resistance of the O/W interfaces against density changes. • GA addition improved flow and storage stabilities of Pickering emulsions.