Interaction of soy protein isolate with vitamin B₁₂ during digestion: Focus on the binding mechanism, structure, and functional properties

This study investigated the release mechanism and digestive characteristics of soy protein isolate (SPI)-loaded vitamin B₁₂ during digestion. According to the molecular docking results, vitamin B₁₂ interacted with the SPI through a hydrophobic pocket on the SPI surface. Spectroscopy revealed that the fluorescence intensity of the SPI and complex system increased with the digestion time. The maximum emitted wavelength was red-shifted in gastric digestion and blue-shifted in intestinal digestion. Moreover, volume exclusion chromatography unveiled that high-molecular-weight proteins in the SPI and complex system gradually decomposed with an increase in the digestion time. The molecular weight progressively shifted from 100 kDa (macromolecules) to 30-50 kDa (small molecules). The present study clarified the digestive mechanism of the SPI with vitamin B₁₂ and offered a theoretical basis for applying the SPI-vitamin B₁₂ complex in food systems.