Abstract: Acer truncatum Bunge. seed protein (ABPI) and salt extractable protein (ABSPI) were extracted from the seeds of A. truncatum Bunge. by using alkali dissolution acid precipitation method and salt extraction method, respectively. Their nutritional and physicochemial properties were compared. The results showed that both ABPI and ABSPI contained the eight essential amino acids (EAAs) with glutamic acid being the most abundant amino acid, accounting for 37.86% and 38.45% of the total amino acid content, respectively. The surface hydrophobicity (664.86), total sulfhydryl content (35.79 μmol/g) and disulfide bond content (11.50 μmol/g) of ABPI were significantly higher than those of ABSPI (P < 0.05), and the thermal denaturation temperature was 128.05 ℃, which was also higher than that of ABSPI (118.33 ℃). The water-holding capacity (4.64 mL/g) of ABSPI was significantly higher than that of ABPI (2.46 mL/g) (P < 0.05), while the oil-holding capacity (3.58 mL/g) was lower than that of ABPI (4.82 mL/g). The foaming capacity, foam stability and emulsifying properties of ABPI showed similar trends to ABSPI with pH. Fourier transform infrared (FTIR) spectroscopy showed that both ABPI and ABSPI displayed typical protein absorption peaks, but the tertiary structure of ABSPI was incomplete. The results of scanning electron microscopy (SEM) showed that the microstructures of the two proteins were significantly different. ABSPI showed an ordered cluster of globular proteins, while the structure of ABPI was dense tight and the surface was irregularly ridged. ABPI had better physicochemical properties and functional characteristics than ABSPI.

Key words: Acer truncatum Bunge. seed protein; physicochemical properties; alkali extraction and acid precipitation; salt extraction