A Spanish Lab Reads Olive Oil With Magnetic Resonance
A chemist at the University of Castilla-La Mancha says nuclear magnetic resonance can identify the fatty acids and other compounds in olive oil quickly enough to tell one variety from another, and to help spot oil that is not what its label claims. The work, by Professor Andrés Moreno in Ciudad Real, covers olive oils and Manchego cheese from the region. Here is what was reported this week, how it compares with the tests labs use today, and why I would not expect it to replace them any time soon.
What was reported
Óleo Revista reported on Wednesday that Moreno, who teaches organic chemistry in the university’s Faculty of Chemical Sciences, has developed a method using nuclear magnetic resonance (NMR) to identify fatty acids and other metabolites in foods with a protected designation of origin, olive oil and Manchego cheese among them. His study carries the unwieldy title “Analysis and reactivity of fatty acids and unsaturated mono-, di- and triglycerides by nuclear magnetic resonance in cheeses and oils of the region”.
The claim is that NMR spectroscopy is “a very valuable tool” because it can detect, identify and quantify different metabolites in complex samples such as food “quickly, simply and effectively”, and that it makes it possible to characterize and discriminate between varieties. Olive Oil Times, which picked up the story today, added that the project was partly funded by the regional government of Castilla-La Mancha and that the group bought a magnetic resonance instrument worth 900,000 euros. Moreno’s team belongs to the university’s Regional Institute of Applied Scientific Research.
One small correction to some of the English coverage: this is not a hospital scanner. NMR spectroscopy is the laboratory cousin of medical MRI, and chemists have used it for decades to work out the structure of molecules. What is new is applying it routinely to regional foods.
How labs check fatty acids today
The fatty acid profile is one of the basic tests every olive oil lab runs. Olive oil is mostly oleic acid, with smaller amounts of palmitic, linoleic, stearic and others, and each has limits set by the International Olive Council. An oil with too much linolenic acid, for example, is a sign that something from outside the olive has found its way in. Our piece on the fatty-acid profile explains what the numbers mean.
The standard method is gas chromatography: the fats are converted into methyl esters and separated in a long column. It works, and it is recognized everywhere, but it takes careful sample preparation and a trained operator.
| Gas chromatography | NMR spectroscopy | |
|---|---|---|
| Status | Official method in trade standards | Research method |
| Sample preparation | Chemical conversion needed | Faster and simpler, according to the researchers |
| What it gives | Percentage of each fatty acid | A broad fingerprint of many compounds at once |
| Equipment cost | Far lower | High (this one cost 900,000 euros) |
Why it matters, and why to keep expectations modest
The appeal of NMR is the fingerprint. Instead of measuring one family of compounds, it shows a great many at the same time, and a computer can compare that pattern with known samples. That is how researchers hope to confirm variety and origin, which the standard tests cannot do. For a designation of origin trying to protect its name, that is a real prize.
- It needs a large library of authentic reference samples, harvest after harvest.
- Results have to be accepted by regulators and courts before anyone can be fined on them.
- The instrument is expensive, so it will sit in a few central labs, not in every mill.
None of that makes the research less interesting. It simply means the classic tests, such as the sterol analysis that catches seed oils, will be doing the heavy lifting for years yet. And the most common problem on the shelf is not an oil from the wrong variety, it is a tired or defective oil sold one grade too high, which is a matter for the tasting panel as much as the chemist. Our explainer on how olive oil adulteration really works sets out the difference.
Every new test gets announced as the end of fraud, and every time the smarter blenders simply learn where its blind spots are. What actually changes behavior in the trade is not the cleverness of the method but how often somebody pulls bottles off a shelf and runs it. A modest test used every week does more than a brilliant one used twice a year.
Sources
- Óleo Revista, “Un investigador de la UCLM desarrolla una metodología para detectar ácidos grasos en el aceite de oliva” (September 15, 2010)
- Olive Oil Times, “Using MRI to Measure Fatty Acids in Olive Oil” (September 19, 2010)