Proteins Extraction and Characterization in Spirulina Biomass: A Comparative Study of High-Pressure Homogenization and Alkaline Methods

The growing demand for sustainable proteins has driven interest in Limnospira platensis (Spirulina) due to its high protein content. However, the presence of the cell wall limits the availability and recovery of proteins within it. Conventional alkaline extraction is widely applied but often results in low yields and excessive solvent consumption. This study compares the efficiency and functional properties of Spirulina proteins extracted using an alkaline method and high-pressure homogenisation (HPH) at 20, 50, 80 and 100 MPa. Following isoelectric precipitation, proteins were collected in precipitate and supernatant fractions and characterized for yield, solubility, phycobiliproteins content, emulsifying and foaming properties, water– and oil–holding capacity, thermal stability and rheological behaviour. Microscopy confirmed progressive cell disruption with increasing homogenization pressures. HPH at 50 MPa increased protein extraction by 28% compared to alkaline extraction and significantly (p < 0.05) improved solubility, oil-holding capacity, foaming and emulsion properties. Phycobiliproteins, particularly C–phycocyanin, were more efficiently recovered in HPH supernatants, achieving a higher purity index than the alkaline method. Rheological analysis showed weak gel-like network formation, whereas excessive mechanical stress reduced functionality. Overall, HPH emerges as an interesting method for obtaining Spirulina proteins with enhanced technological properties; however, pressure optimisation is required to avoid denaturation and functionality loss.