Alkaline solubilization of microalgal protein and its impact on the functional properties of protein extract

Abstract

Microalgal alternative proteins are increasingly recognized as a sustainable and promising source for future food production. Despite the widespread use of alkaline solubilization in protein extraction, its influence on the functional properties of microalgal protein extracts has received limited attention. This study marks the pioneering effort to assess the impact of alkaline (NaOH) solubilization on both the extraction process and the functional properties of Chlorella vulgaris protein extract (CVPE) obtained through isoelectric precipitation. With the gradual escalation of alkaline concentration from 0 to 0.7 M, there was a notable improvement in protein extraction efficiency, increasing significantly from 6.22% to 56.23%. However, elevated NaOH concentrations resulted in protein degradation, as evidenced in SDS-PAGE studies. Alkaline solubilization exhibited a positive impact on various functional properties of CVPE. It enhanced solubility, water absorption capacity, foaming capacity and stability, as well as emulsifying activity and stability. However, there was a slight decrease in oil absorption capacity with increasing NaOH concentration. Notably, the maximum solubility, oil adsorption capacity, foaming capacity, and emulsion activity of CVPE were 2.3-, 1.8-, 2-, and 1.3-fold higher, respectively, than those of commercial soy protein isolate (SPI). This highlights the effectiveness of alkaline solubilization in in modifying C. vulgaris protein and emphasizes the high potential of CVPE as a functional food ingredient.