The researchers purchased a total of 36 private-label avocado oils, labeled both as refined (29) and virgin/extra virgin (7), from 19 grocery retailers across the U.S. and Canada. The private-label products were produced by a third party processor and sold at various price points under a grocery store or retailer brand label.

The samples were tested and graded for quality, referring to the freshness of the oil, and purity, which was measured by fatty acid, sterol, and other profiles that differentiate avocado oil from other oils. A total of 31 percent of the samples tested were pure, and 36 percent were of advertised quality. Specifically, only three refined samples and one virgin/extra virgin sample passed both purity and quality standards.

Although the researchers found that lower-priced oils were more likely to be adulterated, cost is not a guarantee for purity or quality. The best way to determine if an avocado oil is pure, according to the researchers, is a combination of approaches including fatty acid profile, sterols profile, and the possible addition of triacylglycerols (TAGs). For quality, the researchers suggest using free fatty acidity (FFA) and peroxide value (PV), with the potential of PV being replaced by ultraviolet (UV) absorbance.

The study revealed trends in the adulterated oils that professional buyers can reference to make more educated choices regarding suppliers. For example, a slightly elevated stearic acid value accompanied by slightly elevated delta-7-stigmastenol and delta-7-avenasterol indicates likely adulteration with a seed oil, usually sunflower or safflower. Additionally, most adulterant oils have low palmitoleic fatty acid content, so if other indicative trends are seen alongside low palmitoleic content, adulteration is probable.

Furthermore, if high oleic acid content is observed in tandem with aforementioned trends, the adulteration is likely to be with high oleic safflower or high oleic sunflower oil, rather than with canola or soybean oil. Elevated brassicasterol points to adulteration with canola oil, especially when it is accompanied by low palmitic acid.

In general, the greater the number of fatty acids and sterols that are not in acceptable ranges and the more significantly that each is out of range, the more likely that adulteration is occurring.

Overall, the study’s findings indicate that, since the release of the first UC Davis on avocado oil in 2020, there are still issues with purity in avocado oil and these issues extend significantly into private label oils. However, some progress has been made, and there has been a coordinated effort by researchers, industry leaders, and government agencies to establish enforceable standards. For example, the Avocado Oil Expert Group was formed in collaboration with the American Oil Chemists’ Society to discuss potential standards and future research projects.

The UC Davis researchers hope that the study’s findings will aid the establishment of standards that benefit both consumers and avocado oil producers. The team will continue to study how natural factors such as avocado type, harvest times, geographic origins, and processing methods could affect the chemical composition of avocado oil, with the aim of contributing to the creation of standards that will accommodate natural variations while detecting any adulterations.