Haematococcus pluvialis soluble proteins: Extraction, characterization, concentration/fractionation and emulsifying properties

A water-soluble matrix was extracted from green vegetative Haematococcus pluvialis through high-pressure cell disruption either at native pH (5.7) or with pH shifting to neutral (7). The resulting supernatant is mainly composed of carbohydrates and proteins, with the highest yield of proteins obtained at neutral pH (73 ± 2% of total biomass proteins). The key emulsification properties of the proteins isolated in neutral supernatant (emulsification capacity (EC): 534 ± 41 mL oil g−1 protein, emulsification stability (ES): 94 ± 3% and emulsification activity index (EAI): 80 ± 1 m2 g−1) were comparable to the native supernatant values (EC: 589 ± 21 mL oil g−1 protein, ES: 84 ± 3% and EAI: 75 ± 1 m2 g−1). Confronted to sodium caseinate (EC: 664 ± 30 mL oil g−1 protein, ES: 63 ± 4%, and EAI: 56 ± 4 m2 g−1) these results highlighted the strong potential of proteins isolated from H. pluvialis as emulsifier agent. Moreover, experiments have shown that the stability of emulsions obtained from supernatants is due to the proteins rather than the carbohydrates.