Two earlier blog posts (links at end of post) on the adulteration of olive oil have featured four research studies using HPLC, Charged Aerosol Detection, and Electrochemical Detection in their work, and now I am pleased to present an improved global HPLC method for the detection of adulteration in olive oil developed by researchers in our Chelmsford Massachusetts office!
To start with, why is the adulteration of olive oil such an important food safety concern? By the way, it turns out this concern is not new. Archeologists have found clay tablets in Syria that have been dated to 2,400 B.C. which cover rules for olive oil production and anti-fraud regulations! (Link to site whyoliveoil.com)
Olive oil, high in monounsaturated fatty acids, is a key component of the heart-healthy Mediterranean diet recommended by doctors and, as a result, has become increasingly popular in populations that have not historically consumed this oil. But, not all olive oils are nutritionally the same; there are a number of commercial grades of olive oil differing in quality, nutrient levels, antioxidant activity, and final chemical composition.
Here are the categories of olive oil commonly sold on the market:
- Virgin olive oil is the juice of freshly harvested olive fruits.
- Extra virgin olive oil (EVOO) is of the highest quality based on both sensory and physical–chemical characteristics.
- Refined olive oil is oil that has been chemically purified.
- Commercial olive oil is a blend of virgin and refined oils.
- Pomace olive oil is obtained from the solid remains of olives already pressed for juice using solvent extraction.
Unfortunately, as consumer demand for EVOO is set to outpace production, the inevitable increase in EVOO price makes it an ideal target for adulteration. Adulteration can take many forms. The ones that impact health the least are those that maintain the safety of the product such as passing off inferior olive oil as superior olive oil, or blending olive oil with cheaper oils such as sunflower, soybean, sesame, rapeseed, canola, corn, palm, and hazelnut. The most serious form of adulteration compromises the health of the consumer, for example, over 600 people died from toxic oil syndrome (link to Wikipedia) in the early 1980s after consuming rapeseed oil adulterated with aniline that was labeled as Spanish olive oil. Also, blending olive oil with peanut oil is of concern for those with peanut allergies.
Like what you are learning?
To help tackle the problem of olive oil adulteration, we developed a simple HPLC-based method described in poster note,Determination of Olive Oil Adulteration by Principal Component Analysis with HPLC–Charged Aerosol Detector Data, (downloadable PDF), using charged aerosol detection to generate patterns of fats (triglycerides) found in oil samples. These patterns can be used to determine pure EVOO samples from olive oil blended with corn, hazelnut, or pomace. Simple dilution does away with extensive sample preparation often required for other approaches.
By the way, if you are looking to determine different lipid classes, such as steroids, free fatty acids, free fatty alcohols, phytosterols, mono-, di- and tri-glycerides, or phospholipids, do check out this poster note, Novel HPLC-Based Approach for the Global Measurement of Lipids (downloadable PDF). The poster describes several HPLC methods for the determination of lipid classes in a single run using the same HPLC system and charged aerosol detector mentioned above. The advantage of using the charged aerosol detector is that it is a mass-sensitive detector capable of directly measuring any non-volatile and many semi-volatiles analytes. Analytes give similar response independent of chemical structure, an advantage when compounds are not commercially available.
More resources for that will help address challenges in testing olive oil:
- HPLC, CAD, & ECD Authenticates Olive Oil (blog post) provides links to an interesting podcast featuring fraud in olive oil, a link to the International Olive Council for olive oil standards, and links to three published research articles.
- HPLC & Electrochemical Detection: Polyphenols in Olive Oil (blog post) provides links to a couple of stories on olive oil fraud and a link to a research study that tested samples from nine countries on four continents.
- Discriminating olive and non-olive oils using HPLC-CAD and chemometrics (link to abstract). Research article describes the characterization of triacylglycerides in 126 samples of olive, corn, sunflower, peanut, soybean, canola, rapeseed, grape seed, sesame, and mixed oils.
- A validated method for the determination of selected phenolics in olive oil using high-performance liquid chromatography with coulometric electrochemical detection and a fused-core column (link to abstract). Research article describing the quantification of phenolics tyrosol, hydroxytyrosol, oleuropein, pinoresinol, and caffeic, ferulic, vanillic, and p-coumaric acid in olive oil.
Do enter your questions on the method or the systems used in the Comments box below; our experts look forward to hearing from you.