Co-precipitated protein prepared by soybean protein and phycocyanin: Focus on protein structure and nutritional...

Studies on the soybean-algae co-precipitated proteins remain limited, particularly regarding their nutritional quality. We investigated the differences in structure and nutritional characteristics of soy-phycocyanin co-precipitated protein (Co), soy-phycocyanin blended protein (BL), soy protein isolate (SPI), and phycocyanin (PC). Compared with BL, Co had higher α-helix and β-sheet content, smaller particle size and ζ-potential, with unique "chain network" structures. Co was mainly stabilized by hydrogen bonds, hydrophobic interactions, and electrostatic interactions. Compared with SPI, PC, and BL, the digestibility of Co was the highest (98.46%, intestinal). Furthermore, Co exhibited a more balanced amino acid composition, with significantly higher contents of essential amino acids (sulfur-containing amino acids: 43.60 mg/g; Histidine: 32.29 mg/g). Co showed more unique proteins (139 kinds) after digestion. In conclusion, the co-precipitation treatment could improve the nutritional quality of composite protein system. This study provides a new theoretical basis for developing composite protein products with enhanced nutritional quality.