Continue
By using our website you accept our cookies policy.Find out more

The acid test

Posted on 28/03/2018

How to make sure extra virgin olive oil does what it says on the tin.

Many people buy extra virgin olive oil because of its associated health benefits. But few may realise that in fact, a third of olive oils tested in the UK last year were found to be of insufficient quality.

This finding tied neatly into an Innovate UK-funded research project by optical sensor specialists Liquid Vision Innovation to investigate the technical challenges and cost benefits of associated with the use of sensor technology to secure the olive oil supply chain.

“That number is based on only around 65 tests a year,” said Cathy Rushworth Curran, Chief Scientist at Liquid Vision, “The tests are laboratory based, and the cost for doing the required EU regulatory testing can be about £600 per sample. At the moment, the only olive oil testing that happens is one per 1,000 tonnes of imported olive oil. So you can imagine that, although the failure rate is very high, the amount tested is very low, meaning that it’s hard to make an accurate assessment of the quality of the majority of extra virgin olive oil that we consume. This is because of the high cost of measuring.”

For Rushworth Curran, who spoke at KTN’s Food Industry Innovation 2018 event, sensor technology offers a tremendous opportunity to increase the quality of the olive oil supply chain. Current testing of olive oil coming into the UK is limited to a low number of grab samples – and while the oil is subject to some instances of tampering (olive oil tops the list of the 10 foods most at risk of fraud in the EU), the biggest issue may be the the degradation that happens during transit and storage.

“Olive oil is degraded with heat and light and with oxygen,” said Rushworth Curran. “So when you’ve got olive oil stored in transparent plastic bottles on supermarket shelves, even if it was extra virgin olive oil grade when it arrived, it may not be by the time you’re consuming it. It’s not necessarily a health hazard – it’s more that you won’t be getting the health benefits that you expect. If you’re not consuming high-quality extra virgin olive oil, then you’re not getting any of the health benefits, you’re just getting the fat content.

“Because it’s a year-on-year production, the amount of olive oil that’s produced varies and, although it’s treated like a cooking oil, it should be considered more as a fruit juice, so it actually should be consumed fresh. As it ages, then the nutritional benefits of olive oil tend to decrease over time. When you have something that has been stored for a long time, it won’t be as good quality as the olive oil that it was when it started.”

Liquid Vision’s solution involves putting optical sensor technology closer to the point of sale.

One of the key issues in the UK, said Rushworth Curran, “is that we only monitor to meet the EU requirements, because that’s the funding that comes to Defra, and they measure the one test per 1,000 tonnes of olive oil, and that’s shown that a third of those failed, so what you really need is something that can give you a more rapid indicator, at a much lower cost, of whether the olive oil is actually good quality or not.

“Doing that is always going to be a compromise, because obviously you’ve gone from a range of complex laboratory-based tests defined in the EU regulations, including organoleptic characterisation by 8-12 tasters.

“However, optical sensors are attractive monitoring tools because they can provide real-time data that can inform directly on product quality. In particular, direct sample analysis without using the use of any solvents or the requirement for dilution means that you can give the instrument to a non-specialist operator – so you can imagine somebody in a supermarket could use that as a check, and ultimately down to the consumer if the sensor could be made low cost enough.

“We’ve found that we can certainly see the differences between extra virgin olive oil and more refined olive oils. But more importantly, in the extra virgin olive oil class, we can see huge variation between samples. What’s particularly interesting there is that the anti-oxidants in extra virgin olive oil have some unique optical character, so what we’re hoping is that we can use the optical data to infer quality of what should be there and what shouldn’t be there. In particular, the many polyphenols have a fluorescence signature, which we are hoping to detect.”

Liquid Vision has recently received Horizon 2020 funding through the INCluSilver project to do a more detailed investigation on the polyphenol content of extra virgin olive oil, with a focus on healthy ageing and personalised nutrition.

Its potential customers are not just supermarkets, but every point in the olive oil supply chain. And until those sensors are affordable enough for consumers themselves, Rushworth Curran has some words of advice: buying your extra virgin olive oil in tins, not plastic – and keeping it away from the stove, will keep it fresher for longer.