Achieving high-performance peptide-based foam via moderate hydrolysis and zinc coordination of oat proteins

Currently, developing natural macromolecule-based liquid foam with high foaming performance remains a challenge. This study demonstrated that zinc ion coordination (16:1 mass ratio of peptide to ZnSO4) considerably improved the foaming performance of oat peptides (OP), a 75-min hydrolysate of oat globulin. In particular, the coordination complex (OM–Zn; 10 mg/mL) of the 3–10 kDa peptides (OM) and zinc ion exhibited foaming ability and half-life (t1/2) of 190.3% and 30.6 h, respectively, with its t1/2 15.7-fold longer than that of OP. Further investigations revealed that zinc coordination induced OM assembling into high-amphiphilic (88.5°of θo/w) and low-surface charge (−6.5 mV) supramolecules through the formation of coordinate and hydrogen bonds, allowing the OM–Zn particles to have high apparent viscosity (64.7 Pa s), shearing resistance, and interface absorption capacity (30.2 nN of adhesion). Compared to egg white (11% protein), OM–Zn (1% protein) had (a 1.3-fold) larger foaming volume and stronger foaming fabricability. Meanwhile, the OM–Zn foam could also absorb and release hydrophobic and hydrophilic molecules, and the rifampicin-loaded OM–Zn foam effectively released the drug to 62% in 30 h, superior to currently drug-loaded nano-systems. These findings implied the potential of OM–Zn as a foam for food and drug delivery and established a groundwork for using green peptide-based functional foam as a substitute for their synthesized counterparts.