Verifying the purity of olive oil involves checking for official third-party certification seals, such as the USDA organic seal, North American Olive Oil Association quality mark, or the California Olive Oil Council seal, which mandate rigorous laboratory testing. Consumers can also perform a basic refrigerator test, though imperfect, by observing whether the oil solidifies when chilled; however, chemical analysis of free fatty acids, peroxide values, and sensory panel evaluations remain the only definitive methods to detect adulteration with cheaper seed oils.