Spectroscopic analysis of the effect of vitamin B12-soy protein isolate on the soy protein isolate structure

In this paper, the influence of the interaction between vitamin B12 and soybean protein isolate (SPI) on the structure of the SPI was studied by Fourier transform infrared (FTIR), Circular dichroism (CD), and Raman spectra. The results of the FTIR and CD spectra show that when the concentration of vitamin B12 combined with the SPI increases, the β-sheet and irregular curl in the SPI will gradually change into an α-helix and β-turn structure, making the structure of SPI more orderly. In addition, the conformation of amide, the vibrational modes of side-chain amino acids and disulfide bonds, and the vibrational modes of aliphatic C-H bonds of SPI were analyzed by Raman spectroscopy. The results showed that the interaction between SPI and vitamin B12 increased with the increase in the concentration of vitamin B12. At the same time, aggregates were formed between the complexes, which made the structure of the SPI tend to be orderly. This paper provides a basis for the study of vitamin B12 in improving the structure and function of protein, and also provides a theoretical basis for the further study of the interaction between vitamin B12 and protein. •First study to analyze the effect of vitamin B12 on SPI secondary structure.•The changes of protein secondary structure were compared in detail.•Using FTIR, CD and Raman spectrum to analyze the change of complex structure.•Providing a theoretical basis for the development of functional SPI-vitamin complex.