Is the olive oil in your kitchen cupboard FAKE? The 5 key signs your bottle has been padded out with cheap alternatives

Whether you're a Michelin-star chef or a humble home cook, splashing out on a bottle of good olive oil can improve almost any dish.

However, experts now warn that many of us might not be getting what we pay for.

This year, the cost of olive oil has spiralled to £9.49 per bottle on average - 168 per cent higher than in January 2021.

This has led unscrupulous producers to bulk out their products with cheaper oils - including some considered unfit for human consumption.

Luckily experts say there are five key signs which show whether your olive oil is real.

What is fake olive oil? 

Olive oil fraud can take a number of different forms but generally involves two types of adulteration. 

Either, producers take lower-quality olive oils and mislabel them as high-quality products such as extra virgin olive oil.

Or, in many cases, olive oil is mixed in with cheap neutral oils such as sunflower or rapeseed oil to stretch it further.

In some cases, batches of cheap oils are dyed with green chlorophyll and yellow carotenes to make them appear like olive oils.

Due to a series of poor olive harvests, the price of olive oil has increased dramatically in recent years - more than doubling since 2018.

Professor Maurizio Servili, an olive oil expert from the University of Perugia, told MailOnline that this has created a highly profitable opportunity for forgers.

Professor Servili says: 'Olive oil is not a cheap product. It's easier and more economical to make frauds of an expensive product than a cheap product.'

In the first three months of this year, the EU recorded a record number of 'cross-border notifications' for olive oil mislabeling.

In total, 50 cases of potential fraud were reported compared to just 15 in 2018.

However, these figures omit domestic cases and are likely to underestimate the true scale of the issue.

While much of the forgery is small scale, some is conducted on an industrial scale by organised criminals such as the mafia.

In July this year, Italian authorities confiscated 42 tonnes of fake olive oil worth €900,000 (£750,000).

In the same raid, the police also uncovered a further 71 tonnes of an 'oily substance' and 623 litres of chlorophyll used to dye the oils.

But even against such sophisticated fraud operations, there are still ways to ensure you don't get duped.

How to find real olive oil  

The only way to know for certain if your olive oil is fake is with laboratory testing.

However, there are also several ways for you to separate the frauds from the real deal at home.

Most of us might have never thought to taste the olive oil we cook with, but experts say that flavour is one of the best signs that oil has been tampered with.

Judy Ridgeway, an independent olive oil expert and author, told MailOnline: 'When you refine an oil, what happens is that you strip it of all taste and flavour of any kind.

'So the first thing you might look at is a note which has very little flavour. An oil which is really lacking in flavour is suspect.'

Pour a small amount of oil into a clean glass and take a sip, letting it coat your tongue fully - you can always spit it out after if you don't fancy drinking any oil.

Real extra virgin olive oils should have a flavour which is peppery and bitter, with notes of sweetness and fruit while an adulterated oil is more likely to have little or no flavour. 

However, a tasteless oil is not always a conclusive sign of forgery, as Ms Ridgeway says that some real extra virgin olive oils can also be bland and boring.

To be sure you don't end up buying any fake oil in the first place it's equally important to think about where you buy it.

You might think that the safest option would be to take a trip to Italy or Spain and get oil directly from the source.

However, Ms Ridgeway says that you are 'much more' likely to end up with a fraud while abroad.

Under EU legislation, although it is illegal to mislabel oil, there's no requirement for producers to have oil tested before it is sold.

This means that a local producer in Italy is more likely to be selling faulty or fraudulent oils than an exporter which faces rigorous border inspections.

Supermarkets or specialist food stores in the UK are generally much safer in terms of fraud and you are quite unlikely to encounter anything being knowingly mis-sold.

Likewise, you can improve your chances of getting real olive oil further by knowing what to look for on the bottle.

In the UK, only high-quality extra virgin olive oil can legally bear the 'extra virgin' label.

To get the real product, look for bottles that are marked with text which reads: 'Superior category olive oil obtained directly from olives and solely by mechanical means.'

Additionally, look for a DOP, or 'Protected Designation of Origin', seal on the bottle.

This tells you that the oil was produced in a specific geographic area which often has stricter testing regimes than other regions.

Additionally, more reputable oils may provide the name of the olive grower, the exact area where the olives were grown, and the date of the harvest.

Generally, the more traceability the bottle offers for its product the more likely it is to be legitimate.

Finally, keep an eye out for any certificates from third-party testing associations which can guarantee the oil's quality.

American-produced oils may be approved by the California Olive Oil Council (COOC) or the North American Olive Oil Association (NAOOA).

How NOT to test your olive oil 

One of the most popular tests recommended on social media platforms like TikTok is the so-called 'fridge test'.

Social media users claim you can tell if your olive oil is real or fake by placing a small sample in the fridge overnight.

If the olive oil is real, it will supposedly set or become gelatinous while fake oils bulked out with cheap alternatives will remain liquid.

While it might seem odd, there is a core of scientific truth to this strange theory.

Typically olive oil contains high amounts of oleric acid, a monosaturated fat which solidifies at warmer temperatures.

Oils derived from sunflowers or corn, meanwhile, typically contain higher amounts of polyunsaturated fats which only congeal at very low temperatures.

Dr Servili says: 'If you have corn oil which has been sold as olive oil, in this case, the corn oil in the freezer will not be crystallised.'

However, Dr Servili says that this kind of simple fraud is extremely uncommon.

More often, olive oils will be adulterated with smaller amounts of vegetable oil or using oils such as rapeseed which contain similar levels of oleric acid.

This means that some fake olive oils may set when placed in a cold environment.

More importantly, the test doesn't work because not all real olive oil will set in the fridge.

Alexis Kerner, olive oil expert and founder of The Olive Oil Workshop, told MailOnline: 'The fridge test does not work because each olive oil is different and has unique compositions.

'Some fats contained in the oil may solidify at fridge temp and others won't. If it were that easy, all the good producers would be screaming it from their rooftops.'