Effect of Rosmarinus officinalis and Origanum majorana extracts on stability of sunflower oil during storage and repeated heating

Both rosemary (Rosmarinus officinalis) and marjoram (Origanum majorana) are abundant in phenolic compounds, exhibiting exceptional antioxidant activity. This study aims to assess the impact of rosemary and marjoram extracts on the stability of sunflower oil during storage and repeated heating. Sunflower oil supplemented with herbal extracts or butylated hydroxytoluene (BHA) at a concentration of 200 ​ppm was stored for six months under light and dark conditions at room temperature. Peroxide value (PV), p-anisidine value (An-V), and total oxidation (TOTOX) value were measured to monitor lipid oxidation progression. A significant difference (P ​< ​0.05) was observed between light and dark storage for all studied samples regarding oxidation parameters. The ethanolic extract of rosemary exhibited higher antioxidant activity compared to BHA and other extracts. Furthermore, sunflower oil supplemented with the ethanolic extract of rosemary underwent weekly treatment at 100 ​°C for 30 ​min over four consecutive weeks. Although all oxidation indicators increased during repeated heating, the addition of rosemary and marjoram extracts as well as BHA significantly reduced these indicators. These findings demonstrate that both rosemary extracts and marjoram extracts can serve as natural antioxidants in edible oils.