UC Davis

Avocado oil is a high-value edible oil rich in monounsaturated fatty acids and phytosterols. As consumers seek out healthier and more heat-stable cooking oil, avocado oil has been growing rapidly in popularity. However, the combination of high demand and lack of standards of identity making it difficult to ensure oils are of the quality and purity advertised on the label. Economically motivated adulteration that goes undetected can cause authentic, good quality products to be outcompeted in the market and risks consumer health if an unlabeled allergen is added. The goal of this work was to better understand the chemical composition of avocado oil, or its “fingerprint” so appropriate standards of identity could be created, and so improved adulteration detection methods could be developed. The quality and purity of avocado oils available on the United States market were analyzed to identify the biggest issues in the industry. We found that 82 % of avocado oils were either of poor quality (contained high oxidation and/or hydrolyzation products) or were adulterated. Once the need to develop standards was demonstrated, two different grades of avocados from two regions were collected throughout the harvest season and pressed using a laboratory-scale mill to understand how these variables impacted the quality of the oils. Damaged fruits caused a significant increase in free fatty acidity; however, it was also shown that if good quality fruits were used extra virgin oil could be made from either the whole fruit or the mesocarp. The oils described above plus an additional experimental design that incorporated avocado cultivar assessed how purity parameters vary within authentic avocado oils. Region and harvest time contributed to the largest significant differences in fatty acids and sterols profile. Standards need to be wide enough to accommodate different producing regions, which now includes the United States, Kenya, Peru, and South Africa in addition to New Zealand and Mexico while still minimizing the chance for adulterations to go undetected. New methods using triacylglycerols and cis-vaccenic acid were developed to help support adulteration detection in avocado oil. Cis-vaccenic acid has a higher concentration in avocado oil compared to high-oleic seed oils, which are traditionally difficult to detect in avocado oil, and can be used as a marker of adulteration. By combining triacylglycerol analysis with principal component analysis, adulteration can be detected based on the location of an unknown on the plot, providing an alternative way to detect purity without traditional standards. The findings in this work contribute to ensuring the purity, quality, and safety of avocado oils; help regulators and policy makers to better protect consumers; and support the growth of authentic avocado oil sectors.