Protein isolation from blue mussels (Mytilus edulis) using an acid and alkaline solubilisation technique—process characteristics and functionality of the isolates

Abstract

The pH shift method was developed to isolate proteins from low-value raw materials by solubilisation at high or low pH followed by precipitation. In this paper the application of the pH shift method on isolated mussel (Mytilus edulis) meat and whole mussels is reported. Highest protein solubilisation was achieved at pH values of 2.6 and 12. The optimum precipitation pH values were established as around 5.8 following acid solubilisation and 5.2 following alkaline solubilisation. Protein recoveries were 430 and 580 g kg(-1) with the acid and alkaline processes respectively. Using whole crushed mussels, the corresponding recoveries were 310 and 480 g kg(-1). Process modifications to further improve protein recovery resulted in only a marginal increase. Lipid oxidation was not induced during pH shift processing, but heavy proteolysis occurred during the acid process version. Proteolysis could not be prevented by porcine plasma protein. Alkali-produced proteins performed better in all functionality tests compared with acid-produced proteins. The acid process removed slightly more lipids, recovered relatively more cysteine, methionine and lysine and resulted in whiter isolates. The pH shift method can be successfully used to extract functional proteins from mussels and add value to blue mussels unsuitable for human consumption (with or without shells).