Silicon Dioxide Nanoparticles Affect the In Vitro Digestion of Sodium Caseinate but Not the Formation and Functionality of Bioactive Peptides

Silicon dioxide (SiO₂) nanoparticles (NPs) are among the most commonly utilized inorganic NPs in the food industry because of their ability to enhance the quality of a variety of foods. In the present study, the impact of SiO₂ on the NaCN structure and digestibility was examined. The study also aimed to ascertain the bioactive peptide formation as affected by the interactions between SiO₂ and NaCN. The CD spectrum signals in the 250-290-nm region were altered in the presence of SiO₂ at 14 mg/mL, indicating an alteration in the tertiary structure of NaCN. Additionally, the hydrodynamic size of NaCN micelles increased nearly 2-fold upon interaction with SiO₂. Gathering of casein micelles was observed in the presence of SiO₂, especially at high NP concentrations. At the end of the in vitro digestion simulation, SiO₂ led to a reduced proteolysis rate of NaCN from 8.3 mM Leu to 6.9 mM Leu in the stomach and from 17.4 mM Leu to 15.3 mM Leu in the intestine, as revealed by the OPA assay. The observed phenomenon is likely attributed to the aggregation of sodium caseinate following its interaction with SiO₂ NPs, as evidenced by electron microscope imaging. However, there were no significant alterations in the overall peptide profile. Antioxidant, antimicrobial, and ACE-inhibitory properties of the < 3-kDa peptide fraction remained unaffected by SiO₂, which is consistent with a similar peptide profile.