Ionic strength and pH stability of oil-in-water emulsions prepared with acid-hydrolyzed insoluble proteins from Chlorella protothecoides

Abstract

BACKGROUND: Chlorella protothecoides is one of the most widely commercialized and studied microalgae species. Recent research reported improved emulsifying properties of the insoluble protein fraction from C. protothecoides after thermal–acid treatment. RESULTS: In this research, we studied the influence of ionic strength (sodium chloride 50–500 mmol L−1 or calcium chloride 5–50 m mol L−1) and pH (2–9) on the stability of oil-in-water emulsions prepared by 3% (w/w) of the untreated insoluble microalgae protein fraction or hydrolysates obtained after treatment with hydrochloric acid at 65 °C (Hydrolysates 65) or 85 °C (Hydrolysates 85) for 4 h. The emulsions were prepared by mixing 10% (w/w) oil and homogenized at 68.9 MPa. The ionic strength and pH were, subsequently, adjusted. The mean particle diameter of emulsions remained constant despite extensive variations in ionic strength or pH. Emulsion droplets stabilized by Hydrolysates 85 were stable against coalescence at all ionic strengths or pH values tested. CONCLUSION: The results indicate a high potential to use acid-hydrolyzed insoluble microalgae protein fractions for the formulation of various emulsion-based food systems. © 2020 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.