Promoting walnut protein as a precursor of bioactive peptides: The assisting role of high hydrostatic pressure

Innovative high hydrostatic pressure (HHP) technology offers a promising approach to enhance the enzymatic hydrolysis efficiency of plant proteins and boost the bioactivity of hydrolysates. This study aimed to evaluate the impact of HHP (100–400 MPa) on the enzymatic hydrolysis efficiency of walnut protein, with a focus on its potential as a precursor for bioactive peptides. Results demonstrated that HHP significantly promoted the enzymatic efficiency. The degree of hydrolysis (DH) increased by 127.6 % compared to enzymatic hydrolysis at atmospheric pressure, and the proportion of the low-molecular-weight (low-MW) fraction ( < 1000 Da) increased by 16.0 %. Furthermore, HHP followed by enzymatic hydrolysis (HHPFE) was found to be more effective than HHP combined with enzymatic hydrolysis (HHPCE) in promoting enzymatic hydrolysis. Relatively lower pressure was favorable for HHPFE, whereas higher pressure was beneficial for HHPCE. Peptidomic analysis and bioinformatic approaches indicated that HHP enhanced the production of potentially bioactive peptides with antioxidant, ACE inhibition and DPP-IV inhibition. These potent bioactivities were attributed to the positive effects of HHP treatment on walnut protein hydrolysis, such as promoting DH and enriching peptides containing aromatic amino acids for antioxidant, moderate hydrolysis and abundance of vicilin-derived peptides for ACE inhibition, and aiding release of specific peptide fragments for DPP-IV inhibition. Moreover, molecular docking demonstrated that HHP could facilitate the release of specific bioactive peptides encrypted in walnut proteins, such as antioxidant peptides (FYMSWR and SWPAP), DPP-IV inhibitory peptides (RVAPF and RAWYPH), and ACE inhibitory peptides (VQHWIY and FHHPYP).