Extra virgin olive oil contains a whole host of health benefits including anti-inflammatory and anti-oxidant properties... when it's pure.
But a study by the US Davis Olive Center found that 69 per cent of imported extra-virgin olive oils in Calafornia had been cut with cheaper oils, or 'were compromised' in some way, failing to meet high quality standards.
• HOW TO CHECK: Always make sure to check the back of the bottle for the small-print in the ingredients. Pure extra-virgin olive oil shouldn't contain any ingredient other than olive oil. Remember that if it seems too cheap to be the real deal, then it probably is.
2. Orange juice
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It's not just a case of keeping your eyes peeled for the words "concentrate" anymore.
Some orange juices contain as little as 15 per cent real fruit juice, and even then it may be a mix of orange and other fruit juices, along with flavourings and thickening agents.
• HOW TO CHECK: If you want to drink 100 per cent pure juice, watch out for any 'juice drinks' which are likely to be made from concentrate or be a mixture of other fruit juices, and flavourings.
3. Manuka honey
This super-healthy honey - made in New Zealand or Australia - is famous for its anti-bacterial and anti-viral properties.
But a 2014 UK study found that only one out of seven samples of so-called manuka honey was found to have the required amount of the active ingredient, and a year earlier, it was discovered that there was more manuka honey on UK supermarket shelves than had been produced in an entire year.
Many manuka honeys are blended with common, table honeys to reduce the normally high price of the genuine product, which also reduces the health benefits.
• HOW TO CHECK: Always check the label closely. Genuine manuka honeys should have either a UMF or MGO rating on the packaging (this measures the active ingredients inside the jar) and should always say "100 per cent manuka" in the ingredients.
Holly Ryding, senior brand manager for Real Health Manuka Honey, a 100 per cent pure manuka honey that retails for £23.99, added: "Natural, pure manuka honey has a rich golden colour and runny consistency. If it doesn't freely flow out of the jar, then it's often a sign that it has been heated or overly processed.
"A lot of manuka honeys on the supermarket shelves are pale in colour - another sign that it isn't straight from the hive and may have been blended, heated and processed, all of which can damage the active enzymes within manuka."
4. Truffle oil
Not every truffle oil contains real truffle. If you see a bottle that's rather cheaper than you expected, then it may be synthetic.
In fact, many oils don't contain any truffle at all, but are instead just bottles of olive oil mixed with 2,4-dithiapentane, a compound that has the distinctive smell of truffles, according to Priceonomics.
• HOW TO CHECK: Take a good look at the bottle you've bought. The genuine article should only contain two things: olive oil and truffles. If there's anything else in there, then it's likely that what you have came straight from a laboratory. Some people don't mind either way, but if it matters to you, check the label carefully - and be willing to fork out a lot for the real deal.
5. Prosecco
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The sparking Italian white wine made mainly from Glera grapes is a must for any weekend shopping list, but what makes a real Prosecco?
The name Prosecco is a "protected denomination of origin" - which means that Prosecco DOC wines have to be produced in a specific geographical area that is historically renowned for its Prosecco production. Only the producers of this area, who respect the disciplinary guideline of the denomination, can use the Prosecco DOC name. Others are simply sparkling Italian wines.
However, a genuine Prosecco does not always have to be as fizzy as Champagne: it can be frizzante (semi-sparkling) or tranquillo (still).
• HOW TO CHECK: Is there a label of origin on top of bottle (to show the protected origin status)? Does it say Prosecco on the bottle? If not, you've bought a sparkling wine from somewhere in Italy, but it's not authentic Prosecco. Real Prosecco can also only ever be sold in a bottle, so if you purchase it in a can or on tap, then it's also not 100 per cent authentic Prosecco.
Lucia Giavi, general manager of the Prosecco DOC Consortium explained: "Every bottle of Prosecco DOC on the market should have a state mark which guarantees the origin and the quality of the product. The Prosecco DOC wine is easily distinguishable from the state mark which must be applied on each bottle of Prosecco DOC Wine."
