Nutritional, structural and functional properties of protein fractions from tiger nut (Cyperus esculentus L.) seed meal

Nutritional, structural and functional properties of proteins from tiger nut seed meal (TNPF) were investigated in this study. Four kinds of TNPF, albumin (ALB), globulin (GLO), glutelin (GLU), and prolamin (PRO) were obtained through Osborne extraction method, comprising 42.37%, 6.23%, 31.25%, and 5.10% of the total TNPF, respectively. The ratios of essential amino acids to total amino acids in ALB, GLO, GLU and PRO were 43.60%, 38.29%, 42.39%, and 42.82%, respectively. Our results revealed that GLO exhibited the highest in vitro protein digestibility (86.51%), followed by ALB (81.68%), PRO (75.73%), and GLU (60.52%). Further, the analysis of Fourier transform infrared spectroscopy, intrinsic fluorescence spectra, and surface hydrophobicity indicated that the secondary structure and ternary conformation of the four kinds of TNPF were significantly different. Moreover, four kinds of TNPF exhibited their highest solubility, foaming capacity and emulsifying stability under alkaline condition (pH = 12.0) and the lowest near the isoelectric points. Additionally, GLU exhibited the highest foaming ability, emulsification property, and water/oil holding capacity, while ALB showed the highest thermal stability. These findings suggested that GLU extracted from tiger nut seed meal demonstrated excellent nutritional and functional properties, making it a promising food additive to enhance food quality.