This post is part of the Science Tuesday feature series on the USDA blog. Check back each week as we showcase stories and news from USDA’s rich science and research portfolio.
When you plunk down $17.99 for a bottle of your favorite premium olive oil, you’d like some assurance that what you just bought actually is top-quality olive oil. Sadly, there’s a possibility that your high-priced olive oil might be watered down with other, less expensive vegetable oils, such as those from safflower or canola.
Fortunately, the scientists of the Agricultural Research Service (ARS) are helping ensure that what you get is what you paid for.
Two ARS scientists have developed analytical ways that can be used to assure the authenticity of olive oil, thus allaying consumers’ fears.
Testing olive oil for authenticity requires only a tiny amount of oil—about one-fifth of a teaspoon. The test is also comparatively inexpensive and quick, taking no more than 2-1/2 hours from start to finish, and requires only the equipment and supplies that most DNA labs already have on hand.
The test relies on technology called “polymerase chain reaction” or PCR to compare olive DNA to that of two other kinds of plants, canola and sunflower, whose oil is sometimes used to dilute olive oil. The test focuses on key regions of two genes, known as matK and psbA-trnH, that occur widely throughout nature, including in numerous everyday sources of edible vegetable oil.
The ARS scientists have shown that the DNA sequence of specific regions of these two genes provides a reliable basis for comparison, and can be used to quickly unmask non-olive oils in a sample. The test can distinguish between the three oils at concentrations of 5 percent or higher.
It’s hoped that with further refinements, the test will someday be able to recognize other vegetable oils such as avocado, hazelnut, soybean and walnut that also are sometimes added to incorrectly labeled olive oil.
