Extraction of pumpkin seed oil bodies as natural O/W emulsions: Physicochemical properties, oxidative stability, and component interactions

Abstract

Pumpkin seed oil bodies (PSOBs) extracted from pumpkin seeds show great potential as naturally occurring O/W emulsions. PSOBs extracted by three different solvents (NaHCO₃ solution, Tris-HCl, and Phosphate-buffered saline (PBS)) were obtained and evaluated. The yield of PSOBs exceeded 40% in all cases, with lipid and protein contents (wet basis) ranging from 64.52% to 74.17% and 2.58%–4.23%, respectively. The PSOBs extracted by NaHCO₃ solution contained the highest levels of exogenous proteins and exhibited the greatest viscoelasticity, while those extracted by PBS showed superior physical stability. All PSOBs exhibited pseudoplastic fluid behavior, transitioning from a solid-like to a liquid-like state as shear rate increased. PSOBs extracted by NaHCO₃ solution displayed spherical oil droplets with intact morphology under fluorescence microscopy. PSOBs extracted by PBS showed intense lipid oxidation, and PSOBs extracted by NaHCO₃ solution underwent mainly protein oxidation, while PSOBs extracted by Tris-HCl showed slower lipid oxidation and lower carbonyl content. Additionally, the extraction methods influenced the interconversions between β-structures in the proteins of PSOBs. Changes in the intensity of characteristic peaks near 850 and 830 cm⁻¹ in the Raman spectra indicate Fermi resonance of tyrosine (Tyr) residues, reflecting alterations in the microenvironment of the protein side chain.