Structural properties, antioxidant and immune activities of low molecular weight peptides from soybean dregs (Okara)

•Okara peptides were prepared by high-pressure homogenization-assisted double enzymes.•The method can improve the extraction rate of okara proteins by 69% and 51%.•Antioxidant and immune activity were compared, and HPH-VAP was screened out.•116 okara peptides were identified from HPH-VAP by HPLC-MS/MS.•The release of cytokines IL-6, TNF-α and IFN-γ was elevated. In this study, a method for preparing low molecular weight peptides (HPH-VAP) from okara using high-pressure homogenization assisted double enzymes was proposed. In order to explore its advantages, the effects of various methods on protein extraction rate and on the structure, antioxidant and immune properties of peptides were compared. The results showed that the protein extraction rate of this method was increased by 69% and 51% compared with other methods, and the structure only led to changes in the hydrogen bonds between peptide chains. HPH-VAP was screened out through functional characteristics, its structure was identified by HPLC-MS/MS, and further immunological activity analysis was carried out. The results showed that it promoted cell phagocytic ability, NO level and release of cytokines IL-6, IFN- γ, TNF-α. Therefore, this method is an effective and applicable method for industrial preparation of okara peptides, and has a positive effect on the reuse of okara resources.