Enzymatic extraction and physicochemical properties of Porphyra haitanensis protein

Abalone viscera is rich in hydrolytic enzymes that can decompose algal polysaccharides. In order to realize the highly efficient extraction and industrial production of Porphyra haitanensis protein, we used abalone visceral enzymes to break the cell wall of P. haitanensis to extract porphyra protein, and compared the physicochemical properties in proteins prepared by freeze drying and air drying. The results show that the optimal enzymatic conditions were obtained as follows: enzyme dosage of 7.6%, enzymatic hydrolysis time of 2.8 h, enzymatic hydrolysis temperature of 35 ℃, and material-to-liquid ratio of 1:25. The protein yield under above conditions was (238.65±2.13) mg∙g⁻¹. The results of appearance morphology and cell morphology of Porphyra haitanensis indicate that abalone viscera enzymatic digestion could break down the cell wall of P. haitanensis significantly. Freeze-dried P. haitanensis protein (FPP) showed better solubility and emulsification properties than spray-dried P. haitanensis protein (SPP) at different pHs (P<0.01), while the surface hydrophobicity and contact angle of SPP were higher than those of FPP (P<0.01). Scanning electron microscopy shows that FPP had a smooth lamellar surface, while SPP had a more uniform spherical particle size with grooves on the surface. In conclusion, the abalone viscera enzyme was effective in breaking down the cell wall of P. haitanensis and leaching out the water-soluble proteins. All the prepared proteins had good physicochemical proper ties, while the freeze-dried proteins are better than air-dried proteins.