Stabilization of oil-water emulsions with protein concentrates from the microalga Tetradesmus obliquus

The present work used water-soluble protein concentrates from the microalga Tetradesmus obliquus to stabilize sunflower oil emulsions. Microalgal cells were disrupted by sonication, and proteins were separated from the biomass using two methods, isoelectric and solvent precipitations. The protein extracts were concentrated by lyophilization, and the concentrates were used to produce emulsions with three amounts of Tetradesmus obliquus protein concentrate (TobPC) (0.1, 0.5, and 1.0% w/v). Emulsions were homogenized through sonication and characterized for creaming index, optical microscopy, size distribution, zeta-potential, and rheology. Isoelectric precipitation resulted in TobPC with a high protein content (51.46 +/- 2.37%) and a better dispersibility profile. Emulsion stability was higher for both the isoelectric TobPC and control systems than for the TobPC solvent. Solvent TobPC does not efficiently stabilize emulsions at low protein concentrations that showed microscopically larger oil droplets and flocculation spots. A high phase separation velocity was observed for solvent TobPC, probably due to the higher hydrodynamic droplet diameters. The increase in TobPC content in the emulsions resulted in more stable emulsions for all samples. Therefore, Tetradesmus obliquus protein concentrates are a potential emulsifying agent.

Automated summary

This study utilized water-soluble protein concentrates from the microalga Tetradesmus obliquus to stabilize sunflower oil emulsions. Proteins were extracted from disrupted microalgal cells and concentrated through lyophilization. Emulsions were produced using different concentrations of Tetradesmus obliquus protein concentrate (TobPC) and characterized for stability and physical properties. Isoelectric precipitation resulted in TobPC with higher protein content and better dispersibility. Emulsion stability was higher for both isoelectric TobPC and control systems compared to solvent TobPC, which showed larger oil droplets and flocculation spots. Increasing TobPC content resulted in more stable emulsions. Therefore, Tetradesmus obliquus protein concentrates have potential as emulsifying agents.