Collagen is the most abundant protein of animal origin and the most important compound in the connective tissue which is widely used in the food and beverage industry. In addition, recent research has demonstrated the functional, beneficial, and potential properties of collagen extracted from aquatic wastes as nutraceuticals and for delivery systems of sensitive bioactive compounds. Therefore, the aim of this research was considered to study the structural charachters, antioxidant and functional properties of collagen and collagen hydrolysate extracted from the skin of common grouper (Epinephelus coicoides). In the present experimental study, the collagen sample was extracted by acid and enzymatic method and structural characters were studied by Fourier-transform infrared (FTIR) spectroscopy, Scanning Electron Microscope (SEM) and polyacrylamide gel electrophoresis (SDS-PAGE). DPPH radical scavenging, reducing Power and foam producing capacity also assessed.The results of Scanning Electron Microscope confirmed schistose structure, filamentus network, secondary and third structure, and the good interconnection and uniform porus matrix was noticed. The typical characters for type I collagen, including five peaks (amide A, amide B, amide I, amide II and amide III  are observed in the spectrogram of collagen and collagen hydrolysate, also the preserved triple-helical  structure were comfirmed.

The results of the functional properties and antioxidant activity of collagen from orange-spotted grouper skin also showed that with increasing the concentration, reducing power and DPPH radical scavenging ability increased. Comparing collagen and hydrolyzed sample, the foam producing capacity was proved just for collagen.  Finally, it can be said that collagen and hydrolyzed collagen extracted from the skin of orange-spotted grouper with suitable antioxidant properties, and appropriate functional properties can be mass-produced as a bioactive compound and as emulsifier may be used in the food industry and in the production of Functional foods.