Abstract: The active components of turmeric oil (TO) were analyzed using gas chromatography-mass spectrometry (GC-MS), gas chromatography-ion mobility spectrometry (GC-IMS), and electronic nose. The major components of TO were found to be ar-curcumone (23.09%), curcumone (21.36%), and β-curcumone (14.93%). In order to maximize the stability of TO and to mask its irritating substances, a microemulsion encapsulating it (TO-ME) was constructed by the water titration method. Based on the pseudo ternary phase diagram constructed, the optimal process parameters were determined as follows: TO as the oil phase, Tween-80 as the surfactant, propylene glycol as the co-surfactant, deionized water as the aqueous phase, a mass ratio of surfactant to co-surfactant of 4:1, a mass ratio of mixed surfactant to oil phase of 8:2, and a water content of 70% in the microemulsion. The largest area of the microemulsion region was formed under these conditions. The resultant microemulsion had a pH of 6.81 ± 0.02, a density of (1.053 ± 0.001) g/mL, a polydispersity index (PDI) of 0.27 ± 0.11, and an average particle size of (32.81 ± 14.54) nm. The microemulsion was characterized as an oil-in-water (O/W) type microemulsion, with spherical or ellipsoidal droplets. The prepared TO-ME exhibited good centrifugal stability, storage stability, and resistance to oral and gastric digestion, and could be released and utilized in the intestine. The microemulsion system significantly improved the scavenging capacity of TO against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation radical. In conclusion, microemulsion encapsulation significantly improved the stability and antioxidant activity of TO while effectively facilitating its release and digestion in the intestine. Our research results provide a theoretical basis for the high-value development and utilization of TO.

Key words: turmeric oil microemulsion, pseudo-ternary phase diagram, characterization, bioactivity, in vitro digestion