Olive oil scams are proliferating: How do you spot a fake extra-virgin?

If you order extra-virgin olive oil at the restaurant these days, you better check the label carefully. 

According to Europol, selling fake olive oil has become a "common practice". 

The warning came after authorities seized 260,000 litres of counterfeit product in coordinated raids across Italy and Spain, in November. 

Less than two months later, around fifty restaurants came under investigation for the same reason, in Rome, sparking new alarms.

Some fraudsters are substituting the precious "liquid gold" with much cheaper seed oil.

Seed oil is transparent, so they colour it with chlorophyll, to add green tints, and use carotenoids to obtain yellow traits. This creates an olive oil-ish colour. 

However, even if they look similar, big differences remain.

Seed oil has no flavour or smell, while "olive oil is never tasteless. It can be more or less sweet, bitter or zesty, but will never be tasteless", Food Science professor Maurizio Servili tells Euronews.

"Anyone who has tried olive oil at least a couple of times would be able to tell the difference. It is the Polyphenols that give it its peculiar taste."

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The scam may be a bit harder to spot if seed oil gets mixed with some actual olive oil.

In these cases, "simple analysis can unmask the fraud. Like the fatty acids composition test, or the sterol composition, as well as the spectrophotometric constants", says professor Servili.

It's actually legal, in some countries, to sell this type of blend, but the amount of olive oil in the bottle needs to be clear on the label, and the product cannot be called "olive oil".

Other scams use a mix of olive oil and "lampante oil", which is called this because of its historical use as a fuel in oil