Foaming of acid-hydrolyzed insoluble microalgae proteins from Chlorella protothecoides

Abstract

Microalgae are considered to be a promising alternative protein source after extraction and fractionation. Studies have shown that the insoluble protein fraction possesses interfacial activity and is able to stabilize oil-in-water emulsions after acid hydrolysis. The current work studied the surface pressure and foaming properties of the insoluble microalgae protein fraction obtained from Chlorella protothecoides and two of their hydrolysates. Results showed that the surface pressure of the three used protein fractions increased with increasing protein concentration. Moreover, surface pressure of the insoluble microalgae protein increased after hydrolysis at 65 °C (Hydrolysates 65) or 85 °C (Hydrolysates 85) suggesting an increased foaming capacity of the insoluble microalgae protein fraction after hydrolysis. Hydrolysates 85 had the highest foam capacity, and foams remained stable with a half-life time of over 5 h. Overall, hydrolysis of the insoluble microalgae protein fraction with 0.5 M HCl at 85 °C for 4 h resulted in generation of protein fragments that appear to be very suitable to stabilize air-water interfaces in foam-based foods.