A study of 15 samples of extra virgin olive oils sold to the foodservice channel conducted at the Olive Center at the University of California-Davis found that nine failed the USDA extra virgin sensory standard. That standard is rarely used for quality control purposes by the industry but the study authors noted that "some of the oils were so defective that they were classified by sensory panels as 'not fit for human consumption' under the USDA standard." One of the 15 was also found to have been adulterated with canola oil.

The study examined 21 olive oil samples in all.