The effects of stabilised extracts of sage and oregano on the oxidation ofsalad dressings

The antioxidative activity of sage and oregano either dissolved in ethanol or homogenised with olive oil as a carrier was evaluated in salad dressings . These samples were stored in the dark at ambient temperature and at 40 de greesC, and with light exposure at ambient temperature. Sage and oregano ex tracts were encapsulated in liposomes by ultrasonification or microfluidisa tion, and their structures confirmed by microscopic examination and dye-mar ker carboxyfluorescein. The antioxidant effect of these preparations was ev aluated in salad dressings during storage in the dark at ambient temperatur e, at 40 degreesC and at 60 degreesC. The oxidation process was followed by measuring the formation of conjugated diene hydroperoxides as primary and hexanal as secondary oxidation products, as well as changes in the composit ions of fatty acids and tocopherols. Oregano and sage extracts homogenised with olive oil as a carrier showed higher antioxidative effects than these extracts dissolved in ethanol during storage in the dark at ambient tempera ture and at 40 degreesC. Exposure of salad dressings to light changed the a ntioxidative effect of plant extracts into a pro-oxidative effect. The prep aration of liposomes by microfluidisation showed higher encapsulation effic iency and more homogeneous vesicles than liposomes prepared by ultrasonific ation. Sage liposomes prepared by micofluidisation showed high antioxidativ e effects similar to butylated hydroxytoluene liposomes in salad dressings during storage in the dark at ambient temperature and at 40 degreesC.