Effect of heat treatment on physicochemical state and in vitro digestion of salt-soluble protein from Pacific oyster (Crassostrea gigas)

The current research extracted oyster salt-soluble protein (OSSP) from Pacific oyster (Crassostrea gigas) and investigated the effect of heat treatment (35-100 degrees C) on the physicochemical state and in vitro digestion of OSSP. Gel electrophoresis results indicated that OSSP was mainly composed of myofibrillar proteins. The denaturation temperature and enthalpy of OSSP were 54.88 degrees C and 5.49 J/g, respectively. Heating resulted in significantly decreased protein solubility and increased surface hydrophobicity and carbonyl content of OSSP (P < 0.05). Meanwhile protein oxidation and increasing surface hydrophobicity led to the change of OSSP aggregation state. The results of in vitro digestion showed that the digestion of OSSP was inhibited by protein oxidation and aggregation. However, this inhibition was only reflected in protein content, but not in molecular weight distribution. Proteome analysis indicated that identified peptides mainly came from myosin heavy chain striated muscle, paramyosin and tropomyosin, and the types of peptides were determined by OSSP amino acids composition.