Enhancing Vitamin D3 Bioaccessibility: Unveiling Hydrophobic Interactions in Soybean Protein Isolate and Vitamin D3 Binding Via an Infant in Vitro Digestion Model

In the context of infant growth, vitamin D3 (VD3) is crucial but vulnerable to degradation during digestion, diminishing its efficacy. To address this, dynamic-high-pressure microfluidization (DHPM) was employed on soybean protein isolate (SPI) to produce SPI-VD3 nanoparticles. These nanoparticles exhibited a robust binding affinity (Ka) of 0.166 × 105 L·mol-1 at 80 MPa, closely correlated with peak surface hydrophobicity (H0). Molecular simulations elucidated their formation through electrostatic interactions, hydrogen bonding, and hydrophobic forces. In simulated infant in vitro digestion, the 80 MPa DHPM-treated nanoparticles demonstrated the highest VD3 bioaccessibility. This outcome stemmed from structural alterations in the protein post-DHPM treatment, augmenting its affinity for VD3. Consequently, these nanoparticles enhanced solubility during digestion, facilitating micellization, guarding against gastric acid degradation, and ensuring sustained VD3 release with improved bioaccessibility. This study offers valuable insights into augmenting the bioaccessibility of fat-soluble vitamin, particularly VD3, in infant food development, potentially amplifying its nutritional benefits.