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.