Self-Assembled Pea Protein Isolate Nanoparticles with Various Sizes: Explore the Formation Mechanism

Pea protein isolate nanoparticles (PPINs) were successfully prepared by potassium metabisulfite (K₂S₂O₅). The disulfide bonds were disrupted by K₂S₂O₅, and then the PPINs were formed through self-assembly. The average diameter of PPINs increased from 124.7 to 297.5 nm as the concentration of K₂S₂O₅ was increased from 2 to 8 mM, and the PPINs showed higher ζ-potentials (-32.2 to -35.8 mV) and unimodal distribution. The content of free sulfhydryl groups first increased and then decreased with the fracture and reformation of disulfide bonds. Subsequently, the increase of the β-sheet, which has considerable hydrophobicity, promoted the formation of PPINs. The formation mechanism of PPINs was explored by dissociation tests: hydrophobic interactions maintained the basic skeleton of PPINs, disulfide bonds stabilized the internal structure, and hydrogen bonds existed on the exterior of the particles. This study provided a simple and economical method to fabricate nanoparticles.