en Food Science Food Science پژوهشي Research <strong>Background and Objectives:</strong> Virgin olive oil is a vastly consumed product, with widespread appreciation for its good nutritional and health properties. However, oxidation can reduce its quality. The aim of this study was to investigate how the essential oil of <em>Zataria multiflora</em> (Shirazi thyme) can contribute to the prevention of virgin olive oil oxidation in comparison with the actions of &alpha;-tocopherol and BHT. Furthermore, the synergistic activities of citric acid with <em>BHT, <em>Z. multiflora</em> </em>essential oil, and &alpha;-tocopherol were investigated.<br> <strong>Materials and Methods: </strong>Antioxidant activity of the essential oil was determined using radical scavenging capacity and reducing power assays. Virgin olive oil samples were stored at 60&plusmn;1 &deg;C in closed amber bottles for 16 days. Oxidation levels of samples were determined by measuring peroxide, anisidine, TOTOX, K₂₃₂, K₂₆₈ values, and chlorophyll and carotenoid contents of the samples during the storage period.<br> <strong>Results: </strong><em>Z. multiflora</em> essential oil exhibited a significant radical scavenging capacity and reducing power. Peroxide, anisidine, TOTOX, K₂₃₂, and K₂₆₈ values of samples containing <em>Z. multiflora</em> essential oil were significantly lower than those of the control group (without antioxidants). <em>Z. multiflora</em> essential oil reduced the oxidation of virgin olive oil to the same extent as BHT did. <em>Z. multiflora</em> essential oil was more effective than &alpha;-tocopherol. The synergistic activities between citric acid and the various compounds, i.e. BHT, <em>Z. multiflora </em>essential oil, and &alpha;-tocopherol were 2.42%, 4.74%, 1.28% respectively.<br> <strong>Conclusions: </strong>In general, <em>Z. multiflora</em> essential oil can be considered as natural antioxidant for the stabilization of virgin olive oil against oxidation.<br> &nbsp; Accelerated storage, Oxidation, Virgin olive oil, Zataria multiflora 19 28 http://nfsr.sbmu.ac.ir/browse.php?a_code=A-10-591-1&slc_lang=en&sid=1 Malihe Keramat malihe_keramat@yahoo.com 10031947532846003186 10031947532846003186 No Shiraz University Mohammad-Taghi Golmakani golmakani@shirazu.ac.ir 10031947532846003187 10031947532846003187 Yes Shiraz University Mahmoud Aminlari Aminlari@shirazu.ac.ir 10031947532846003188 10031947532846003188 No Shiraz University Seyed Shahram Shekarforoush shekar@shirazu.ac.ir 10031947532846003189 10031947532846003189 No Shiraz University