Tiny, yet impactful: Detection and oxidative stability of very small oil droplets in surfactant-stabilized emulsions

Sten ten Klooster, Machi Takeuchi, Karin Schroën, Remco Tuinier, Rick Joosten, Heiner Friedrich (Corresponding author), Claire Berton-Carabin (Corresponding author)

Research output: Contribution to journalArticleAcademicpeer-review

6 Citations (Scopus)
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Abstract

Hypothesis: The shelf life of multiphase systems, e.g. oil-in-water (O/W) emulsions, is severely limited by physical and/or chemical instabilities, which degrade their texture, macroscopic appearance, sensory and (for edible systems) nutritional quality. One prominent chemical instability is lipid oxidation, which is notoriously complex. The complexity arises from the involvement of many physical structures present at several scales (1–10,000 nm), of which the smallest ones are often overlooked during characterization. Experiments: We used cryogenic transmission electron microscopy (cryo-TEM) to characterize the coexisting colloidal structures at the nanoscale (10–200 nm) in rapeseed oil-based model emulsions stabilized by different concentrations of a nonionic surfactant. We assessed whether the oxidative and physical instabilities of the smallest colloidal structures in such emulsions may be different from those of larger colloidal structures. Findings: By deploying cryo-TEM, we analyzed the size of very small oil droplets and of surfactant micelles, which are typically overlooked by dynamic light scattering when larger structures are concomitantly present. Their size and oil content were shown to be stable over incubation, but lipid oxidation products were overrepresented in these very small droplets. These insights highlight the importance of the fraction of “tiny droplets” for the oxidative stability of O/W emulsions.

Original languageEnglish
Pages (from-to)1994-2004
Number of pages11
JournalJournal of Colloid and Interface Science
Volume652
Issue numberPart B.
DOIs
Publication statusPublished - 15 Dec 2023

Bibliographical note

Funding Information:
This research was funded by the Dutch Research Council (NWO) , grant number 731.017.301 . We thank the LICENSE project partners and especially Prof. Dr. John van Duynhoven (Unilever and Wageningen University) for useful discussions.

Keywords

  • Cryo-transmission electron microscopy (TEM)
  • Droplets
  • Dynamic light scattering
  • Emulsion
  • Lipid oxidation
  • Microemulsion
  • Nanoemulsion
  • Surfactants
  • Swollen micelles
  • Winsor system

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