Preparation and characterisation of the pearl oyster (Pinctada martensii) meat protein hydrolysates with a high Fischer ratio

The primary aim of this study was to obtain high Fischer ratio oligopeptides from the pearl oyster Pinctada martensii meat via proteolysis. Pinctada martensii meat protein was hydrolysed using seven proteases, with pancreatin showing the most protein recovered (90.30%) and the highest degree of hydrolysis (30.22%). In addition, pancreatin treatment liberated aromatic amino acids (AAA) and preserved branched-chain amino acids (BCAA) in the peptide chain more efficiently than other proteases. In our enzymatic hydrolysis system, the AAA are adsorbed by activated carbon much easier in the form of proteins and peptides compared with the free state. The fraction purified from the pancreatin hydrolysate after adsorption onto activated carbon gave a yield of 38.42% based on nitrogen content. It was composed primarily of low molecular weight peptides and had a Fischer ratio of 24.58, with phenylalanine (Phe) and tyrosine (Tyr) content below 1.2%. This oligopeptide mixture can be used for the assistance treatment of patients with hepatic encephalopathy, phenylketonuria and tyrosinemia according to different dietetic requirement.