Microalgal proteins offer promising functionality for structuring oil–water interfaces, yet their interfacial behavior under varying pH conditions—and the implications for encapsulating microalgal-oil bioactives—remain largely unexplored. This study investigates the adsorption kinetics and interfacial rheology of protein isolates from Chlorella vulgaris and Arthrospira platensis (Spirulina) across a range of pH values relevant to food and nutraceutical applications. Interfacial tension measurements were used to quantify dynamic adsorption and film formation, while dilatational interfacial rheology provided insight into interfacial viscoelasticity and network development.

Marked differences were observed between the two protein isolates in their pH-dependent interfacial behavior. Chlorella proteins exhibited faster adsorption kinetics at neutral and alkaline pH, forming interfacial layers with relatively rapid reduction of interfacial tension. In contrast, Spirulina proteins generated more elastic and structured interfacial films, particularly near their isoelectric region, indicating stronger intermolecular interactions and enhanced film rigidity. These differences were reflected in emulsion formation and stability when encapsulating microalgal oil rich in lipophilic bioactives. Emulsions stabilized with Spirulina proteins showed improved oxidative protection and retention of bioactives, whereas Chlorella-based emulsions offered more efficient initial encapsulation due to their faster interfacial adsorption.

Overall, the results demonstrate that pH critically modulates the interfacial assembly and functional performance of microalgal proteins, influencing both droplet stabilization mechanisms and the efficiency of microalgal-oil encapsulation. These findings advance the understanding of microalgal proteins as natural emulsifiers and highlight their potential for the design of sustainable delivery systems for lipophilic bioactive compounds.

Conference theme: physical properties of food hydrocolloids for enhanced product development