Measuring Quality of Virgin Olive Oil with Spectrometers High demand for extra virgin olive oil made this article a profitable target for counterfeiters. A recent study reported that approximately 65 % of bottles labeled as “Imported Extra Virgin Olive Oil” in the US market are lower grade oils. A test with spectrometer measuring light absorbance can determine if the quality of oil really represents the high standards set for extra virgin olive oils by USDA.