Abstract: Protein isolate (PEPI) was extracted from Pleurotus eryngii by alkali dissolution followed by acid precipitation and the major protein components were isolated by the Osborne method. Their physicochemical and functional properties were studied. Results showed that the protein content of P. eryngii was 17.57% (dry mass), and the mainly protein fraction was albumin (PEA), accounting for 81.12% of the total protein isolate. Both PEPI and PEA contained 18 amino acids with essential amino acids accounting for 40.80% and 40.51% of the total, respectively. The surface hydrophobicity of PEA (265.25) was significantly higher compared to that of PEPI (164.27) (P < 0.05), while the contents of total sulfhydryl group and disulfide bonds were lower, which were 61.53 and 10.39 μmol/g, respectively. The thermal denaturation temperature of PEA (100.98 ℃) was lower than that of PEPI (108.27 ℃) and water holding capacity (1.64 mL/g) and oil holding capacity (5.59 mL/g) were significantly lower than those of PEPI (3.58 and 8.36 mL/g) (P < 0.05). The solubility, foaming capacity, foam stability, emulsifying property and emulsion stability of PEPI and PEA showed similar trend with pH, and were the lowest at pI. Fourier transform infrared spectroscopy (FTIR) showed that the secondary structures of PEPI and PEA consisted mainly of β-sheet and β-turn. Scanning electron microscopy showed that PEPI possessed a honeycomb structure. Compared to PEA, PEPI exhibited better functional properties.

Key words: Pleurotus eryngii, protein isolate, albumin, physicochemical properties, functional properties