Releasing ACE-inhibitory peptides from walnut protein via pulsed electric field: A multiscale mechanism-structure-function investigation

In this study, pulsed electric fields (PEF) treatment was demonstrated to effectively enhance the release of angiotensin converting enzyme (ACE) inhibitory peptides from walnut protein (WP). Results showed that PEF treatment induced protein structure unfolding and exposure of hydrophobic amino acids by disrupting intermolecular hydrogen bonds of WP, resulting in increases in sulfhydryl content (from 11.07 to 15.45 μmol/g), surface hydrophobicity (by 8.64 %), and solubility (from 36.44 to 67.85 %) of WP. Ultra-performance liquid chromatography with electrospray ionization–quadrupole–time-of-flight mass spectrometry (UPLC-ESI-QTOF-MS/MS) results indicated that PEF-treated WP (WP-PEF) exhibited a greater potential for releasing peptides containing Phe, Leu, Trp and Pro at the C-terminus than untreated WP, with respective increases of 34, 20, 7, and 6 in their quantities. Eight potential bioactive peptides were selected from WP-PEF enzymatic hydrolysate (WPH-PEF) based on their superior in silico digestion stability and promising bioactivity profiles. Molecular docking analysis demonstrated that hydrogen bonding and hydrophobic interactions served as the predominant intermolecular forces governing the binding affinity between ACE and the bioactive peptides. Furthermore, network pharmacology results suggested that WPH-PEF exerted its antihypertensive effects primarily through modulating the renin-angiotensin system and ameliorating of vascular dysfunction.