Two tests for standards that have not been adopted by the International Olive Council yielded results that supported the negative sensory results. These tests, known as diacylglycerol content and pyropheophytin, have been adopted in Germany and Australia. They confirmed negative sensory results among the olive oils sampled in this study, with 65 percent of the samples failing the diacylglycerol test and 49 percent failing the pyropheophytin test.

In the report, the researchers suggested that International Olive Council and U.S. Department of Agriculture standards would be more effective in assessing and enforcing olive oil quality if they included the German/Australian tests.

“The best extra virgin oil will smell and taste fresh,” said Flynn. He added that quality oils often show the most recent harvest year on the bottle, and have containers that protect the oil from light and are not dusty or shopworn.

The report recommends that further research should be conducted to investigate chemical markers for sensory defects and determine the effects of minor olive-oil constituents on the oil’s flavor and stability. The researchers also suggest that chemical profiles of California olive oils should be analyzed.

Funding for the new study was provided by Corto Olive, California Olive Ranch and the California Olive Oil Council.

The new report is available online at

About the UC Davis Olive Center

The UC Davis Olive Center was founded in 2008 as the first university-based olive research and education center in North America. As a self-funded university center, it continues the university's century-old effort to assist California's olive producers and processors as their industry enters a renaissance, with novel farming techniques and rising consumer demand for olive oil and table olives. The center's collaborative efforts have produced research in food chemistry, mechanical harvesting, olive fruit fly control, olive processing and sensory evaluation of olive oil. This research provides opportunities for graduate students to receive scientific training and earn advanced degrees.