Modulation of the Chemical Properties, Photostability, and Antioxidant Activity of Turmeric Oleoresin by Propylene Glycol

Curcuminoids from turmeric exhibit beneficial health effects. However, their practical application is limited because of poor stability and solubility. The present study investigated the effects of propylene glycol (PG), a common food additive, on the chemical properties, photostability, and antioxidant activity of turmeric oleoresin (TO). PG significantly improved the solubility and dispersion stability in aqueous solutions (<i>P</i><0.05). PG at 20%－30% concentration effectively prevented pigment sedimentation and maintained pigment integrity similar to organic solvents. PG also improved the photostability of TO in a concentration-dependent manner, extending its half-life under irradiation with fluorescent light (FL) and blue light-emitting diode. The results of high-performance liquid chromatography analysis revealed that TO stored with PG in the dark or under FL irradiation had significantly higher retention of individual curcuminoids (<i>P</i><0.05). In addition, PG conferred a concentration-dependent protective effect on the antioxidant properties of TO, increasing its reducing power in aqueous solutions. These findings suggest that incorporating optimal levels of PG can extend the shelf life of and preserve the quality of curcuminoid-containing products.