Experts say lots of factors determine how quickly an oil deteriorates — from the variety of the olives, to how the oil is produced and stored. Matthias Schrader/AP hide caption

itoggle caption Matthias Schrader/AP

Palestinian women harvest olive trees near the occupied West Bank village of Deir Samet near the town of Hebron. Hazem Bader/AFP/Getty Images hide caption

itoggle caption Hazem Bader/AFP/Getty Images

A Greek farmer drives home with his fresh pressed olive oil in barrels near Alyki, Greece. The country's pure olive oil is hard to find, expensive and poorly marketed, businessmen say. Matthias Schrader/AP hide caption

itoggle caption Matthias Schrader/AP