Reverse microemulsions as nano-carriers of tea polyphenols retard oxidation of Eucommia ulmoides oliver seed oil

Eucommia ulmoides Oliver seed oil, rich in polyunsaturated fatty acids (PUFAs), is susceptible to lipid oxidation in foods. Tea polyphenols (TPs) may effectively retard lipid oxidation in non-polar systems according to the polar paradox theory. In this study, we constructed a TPs-loaded water-in oil (W/O) microemulsion, which is a transparent, spontaneously formed, and thermodynamically stable colloidal system. This system consisted of E. ulmoides oil (38%, w/w), Span80, Tween 80, 1,2 propanediol, water, and TPs (3%, w/w). TPs were encapsulated in water cores of microemulsion, endowing this system with the higher oxidative stability and radical scavenging abilities. The accelerated oxidation assay demonstrated that low-dose TPs (<0.5%, w/w) were more effective in retarding lipid oxidation than that of high-dose TPs. Within 56 d, the peroxide value of TPs-loaded microemulsion increased to 16.479 meq/kg oil at 65 ℃ and that of E. ulmoides oil exceeded the Food Safety standards value within only 45 d. These findings indicate that TPs encapsulated into microemulsion effectively inhibit PUFA-rich oil oxidation. The nano-scale W/O dispersed system favors the protection and practical application of natural water-soluble antioxidants in PUFAs-rich lipid foods.