Physicochemical and Functional Properties of Spirulina and Chlorella Proteins Obtained by Iso-Electric Precipitation

In this study, microalgae proteins (Spirulina and Chlorella) were extracted, characterized, and investigated for their potential techno-functionalities. The proteins from the microalgae biomass were extracted by alkaline solubilization followed by iso-electric precipitation. Subsequently, their physicochemical characteristics (microstructure, thermal stability, secondary structure, and crystallinity) and functional properties (protein solubility, water and oil holding capacities, as well as emulsifying and foaming properties) were investigated. Spirulina biomass resulted in a high extraction yield (37%), giving a protein isolate containing 90% of proteins. Both Spirulina and Chlorella protein extracts displayed high thermal stability. FTIR analysis revealed a clear difference in the secondary structure of the protein extracts. A slight difference in microstructure was noted between the two proteins, but both had small particle sizes and uniform dispersity. Spirulina proteins were more crystalline (53%) than the Chlorella proteins (36%). Spirulina showed better functional properties (protein solubility, emulsifying, and foaming properties) compared to Chlorella. We observed that the Spirulina protein had more water-holding capacity than the Chlorella protein, while the latter also showed appreciable oil-holding capacity. These findings suggest that the microalgal proteins could be useful in the food industry.