Extraction of bioactive compounds from oyster (Crassostrea gigas) by pressurized hot water extraction

Pacific oyster muscle hydrolysates were prepared by pressurized hot water extraction (PHWE) at process conditions ranging 125 °C/20 bar ∼ 275 °C/140 bar to investigate various physico-chemical and bio-functional parameters. Degree of hydrolysis was increased with increasing temperature and pressure and at 275 °C/140 bar, hydrolysis was found to be highest. Glycogen, protein, reducing sugar, and phenolic content of the hydrolysates were increased obtained from 125 °C/20 bar to 225 °C/100 bar, but decreased after raising over 250 °C/120 bar. Total and free amino acid contents were subsequently decreased as temperature and pressure increased over 175 °C/60 bar. Radical scavenging activity and antihypertensive activity was found to be highest at 225 °C/100 bar at which condition, the protein molecular size and carbohydrate molecular weight of the hydrolysates were 15 kDa or lower and 300–1000 Da, respectively. This study suggests the 225 °C/120 bar conditions for bio-functional Pacific oyster hydrolysate preparation.