Extraction, structural and functional properties of Haematococcus pluvialis protein after pigment removal

Protein from Haematococcus pluvialis (H. pluvialis) residues after pigment removal was prepared by alkaline extraction and acid precipitation. And the structural and functional properties of protein extracts were measured and analyzed. The effect of extraction conditions (liquid/solid ratio 10-20 mL/g), pH 10-12 and 25-45 °C (temperature) on the yield of H. pluvialis protein (HP) was carried out using Box-Behnken design. Under optimum extraction conditions: liquid/solid 20 mL/g, pH 11.5 and lower extraction temperature 35 °C, the highest extraction yield (81.36%) of HP was gained, which was close to the predicted value (83.32%). The HP exhibited the better functional properties. The solubility could reach 93.65% at pH 10.0; the foaming capacity and stability were 88.32 and 89.62%, respectively; the emulsifying capacity and stability were 161.52 and 48.2%, respectively; the water holding capacity (WHC) and oil absorption capacity (OAC) were 4.06 and 3.29 g/g, respectively. Fourier Transform infrared spectroscopy (FTIR) data of the HP showed the β-sheet content (30.37%) was the maximum, while α-helix content (14.86%) was the minimum, whereas the content of amino acids was rich in HP. These results demonstrated that the HP had potential use in food industry.