Extraction of Arthrospira platensis (Spirulina) proteins via Osborne sequential procedure: Structural and functional characterizations

The Osborne sequential extraction procedure was performed to extract proteins from Arthrospira platensis (A. platensis). The physicochemical description of the extracted proteins yielded three fractions (albumins (Alb, 51.5 %), globulins (Glb, 2.4 %), and prolamins (Pro, 46.1 %)). No glutelin-like proteins (Glu) were found in this microalga. FTIR spectra displayed the beta-turn, the beta-sheet, and the alpha-helix as the principal structures in the Alb, Glb, and Pro fractions, respectively; the random coil was absent in the Pro fraction. The zeta-potential mea-surements indicated isoelectric points closer to 3.0 and 4.5 for the Alb and Glb protein fractions, respectively. In contrast, the Pro protein fraction displayed a negative charge for pH values from 2 to 10. The Alb and Glb fractions exhibited the highest surface hydrophobicity. The best water-holding capacity was attributed to the Alb and Glb fractions, whereas the highest oil-holding capacity and foam stability were assigned to the Pro fraction. The surface hydrophobicity was positively correlated to the emulsion generation. The Osborne method is a promising procedure to obtain green (Alb), blue (Glb), and orangish-red (Pro) extracts from A. platensis through an environment-friendly process.