Oleogel-structured emulsion for enhanced oxidative stability of perilla oil: Influence of crystal morphology and cooling temperature

In this study, the influence of crystal morphology and cooling temperature on the oxidative stability of oleogel-structured perilla oil emulsion was explored. The formation and distribution of the internal crystals were confirmed by differential scanning calorimetry and polarized light microscopy. All beeswax (BW) crystals existed in the internal phase while stearic acid (SA) crystals appeared in the aqueous phase as well. As the crystal grew, the HPMC/SDS emulsified layers were pierced, leading to release of the SA crystals into the aqueous phase with partial droplet flocculation. As a result, the physical and oxidative stability of the BW-structured emulsion was significantly better than that of SA-structured emulsion. The crystallinity of the emulsion increased with higher gelator concentration. The denser crystal network were more effective preventing the penetration of pro-oxidants into the internal phase, resulting in the stronger the oxidation stability. Processing methods with different cooling temperature affected more of the properties of bulk oleogels rather than the oleogel-structured emulsion for long-term storage. Overall, choosing a gelling agent that forms relatively small crystals and preparing an oleogel-structured emulsion with appropriate crystallinity can effectively improve the oxidative stability of structured emulsion with longer shelf life.