Deciphering the characteristics of soybean oleosome-associated protein in maintaining the stability of oleosomes as affected by pH

- The stability of soybean oleosomes was examined at different pHs.
- The most unstable oleosomes suspension was occurred nearby the pI (pH 4.0-5.0).
- The most stable oleosomes suspension was occurred at pH 9.0.
- Electrostatic repulsion and hydrophobic interaction affected oleosome stability.
- β-Sheets content of oleosome-associated proteins accelerated oleosome aggregation.

The understanding of the behavior of natural oleosomes is very important for leading to advancements in liposome manufacturing. Thus, the aims of this work was to evaluate the stable behaviors of oleosomes with regards to a wide pH range (2.0-11.0) using soybean oleosomes. The conformation changes and surface hydrophobicity of soybean oleosome-associated protein, and as well as ζ-potential and particle size distribution of oleosome were investigated. The particle size and ζ-potential of oleosomes, and surface hydrophobicity of oleosome-associated proteins were found to be readily affected by pHs. The secondary structure of oleosome-associated proteins was more susceptible to alkaline treatment than acidic treatment. The most stable oleosomes suspension was occurred at pH 9.0. The electrostatic repulsion and hydrophobic interaction simultaneously affected the stability of oleosome. At pH 2.0 to 6.0, acidic treatment did not significantly change the secondary structure of oleosome-associated proteins. With an increased treatment pH of 8.0-11.0, the contents of α-helix and random coil structures of oleosome-associated proteins decreased, while the amount of β-sheet structures increased. Results highlighted the interesting fact that the aggregation of oleosomes occurring at different pHs was attributed to the synergistic effects between conformation changes and interaction properties of oleosome-associated proteins.

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