Noncovalent Interactions of Sea Buckthorn Polyphenols with Casein and Whey Proteins: Effect on the Stability, Antioxidant Potential, and Bioaccessibility of Polyphenols

In this work, effect of casein and whey protein interaction on the stability, antioxidant potential, and bioaccessibility of sea buckthorn polyphenols was investigated. The results revealed that casein–polyphenol and whey protein–polyphenol interaction both decreased the in vitro antioxidant capacity of polyphenols. On the other hand, the protein–polyphenol complexes increased the stability of sea buckthorn polyphenols during simulated in vitro digestion. Moreover, both the casein–polyphenol and whey protein–polyphenol complexes exhibited an increased bioaccessibility of polyphenols (60.97–64.97%) in comparison to that of free polyphenolic extract (40.01%). The main bonding force between sea buckthorn polyphenols and the proteins was found to be a hydrophobic interaction, as revealed by ATR-FTIR, UV–vis, and fluorescence spectroscopy. The particle size of casein–polyphenol and whey protein–polyphenol complexes was in the nanosize region (650–983 nm). The low span factors of polyphenol–protein complexes revealed the narrow range of particle size distribution and thus more homogeneity in the particle size. This finding highlights that the interaction between casein and whey proteins with sea buckthorn polyphenols could protect these bioactive compounds against the influence of simulated digestion.