Focus on food analysis and testing: It’s all in the DNA

It may sound surprising, but routine food testing can turn into something akin to an episode of CSI. This is because testing labs are using similar DNA analysis techniques to check the authenticity of foods and for a variety of reasons.

A good example is Basmati rice, which attracts a lower import duty than standard rice. For this reason, unscrupulous sellers may try to pass normal rice off as Basmati. But how can you differentiate between the two? As with a crime scene sample, you need DNA testing.

"We look for genetic markers called 'microsatellites'," says Barbara Wimmer, account sales manager for food analysis at international testing laboratory Eurofins. These are highly repetitive parts of the DNA that are unique to each species of rice. Just as two crime suspects will have different DNA profiles, so will two different species of rice. "Each variety has its own fingerprint," says Wimmer. "We can also identify Thai rice and others."

Not every rice variety can be identified: Wimmer says that Eurofins follows 'market needs' to analyse those that are requested.

In a similar fashion, animal species from tuna fish to Aberdeen Angus beef might need to be analysed and authenticated. A ready meal may claim to contain cod so should not use other, cheaper fish.The test here is slightly different: the lab is looking for evidence (or absence) of a particular species (such as cod), rather than variants within (Basmati vs Thai rice). This type of test is commonly used for animals and vegetables.

Take 'Aberdeen Angus' beef, which is protected by 'regional status'. If a supermarket or butcher is selling this and it goes for a hefty premium a 'paternity test' would ensure that it is genuine. Developing a test requires the participation of the Aberdeen Angus society, which provides DNA samples from all 'sires' in the herd. Any beef sample then tested must be related in some way to a herd member. If there is no link, it cannot be Aberdeen Angus.

While a test for this has already been developed, Wimmer says that it is no longer current, because of the addition of new 'sires' to the herd. Effectively, the 'DNA database' is out of date.

"The test was not requested very often, so we've not continued to develop it," she says. "We're waiting for the society to decide what they want to do."And, as with criminals, DNA testing can be used to solve a wide variety of cases. Cheeses can be analysed, to see if they are what they say they are. (Pecorino, for example, should only contain sheep's DNA, as it is made from sheep's milk.) Similarly, meat can be 'gender tested' because sow meat is preferable to boar meat, just as meat from bulls is more expensive and usually of higher quality.

However, DNA testing is certainly not infallible."Some highly processed foods such as ready meals may no longer contain any DNA material," she says. "In this case, further analysis is impossible."

Trendy food

In a world that seems to work at breakneck speed, the demand for rapid testing is increasing all the time. But this fascination for speed is not compulsory, some argue.

"The cost of rapid testing is still quite high," says Allan Barnes, food microbiology business manager of Wickham Laboratories in Fareham, Hampshire. "Many people are still using classical methods."

And he says that the pace of developing these new tests should also be checked.

"There are too many rapid tests out there," he says. "There are 10 or 15 for salmonella: that's too many. You need to have a choice of two or three."

Rather than depending on speed alone, many companies could benefit from a slower approach through trending analysis. This takes ongoing analytical data and tracks it over time in order to identify patterns.

"When your company gets to a certain size, you need some kind of trending," he says. "You want to make sure that the quality of your product is improving all the time.

Trending can be carried out across the factory, or in specific areas. It can be used to monitor incoming raw materials, track the effectiveness of cleaning or check outgoing product quality. Any major changes over time can be flagged up and investigated.

"It's like an early warning system," he says.

Differently sized companies might use it in different ways: a large sandwich maker, with national distribution, might focus on incoming raw materials; a smaller manufacturer would prioritise the assembly process, he says.

He cites the example of one food processor whose products suddenly started testing positive for raised levels of Listeria at the end of their shelf-life. Such a situation was a huge potential health risk as well as a crisis for the firm. "The company was forced to investigate why this was happening," says Barnes.

Wickham provided a 'visiting service' to help track down the cause, by analysing swabs from a wide range of areas within the factory.

The outbreak was finally traced to the factory's flooring, which was not bonded properly. There were cracks in the floor, acting as "Listeria pockets".

Bad practice had crept in, and containers that were laid down on that part of the floor were being contaminated.

The manufacturer had to stop production in that area until it had been cleaned, and floor repairs carried out. "This is about as bad as it gets, but cases like this are very rare you only see them every few years," he says.

New benchmarks

Contamination control is one of the key jobs of food testing, and recent funding from Europe could see improvements in the way that this is monitored and tested.

Thanks to around euro 11M in funding, the Joint Research Centre in Belgium has expanded its Institute for Reference Materials and Measurements (IRMM), which will develop a far broader range of reference materials than previously available. Reference materials are the 'benchmarks' that laboratories use to calibrate their instruments and ensure that there is agreement between different regions and laboratories. They will contain a specific amount of a substance be it a pesticide, bacteria or other chemical species.

IRMM's brief is to develop reference materials that are needed to support ongoing legislation in the EU, which can be anything from sulphur levels in petrol to pesticide levels in food.

Laboratories use reference materials in two main ways: for internal use, to ensure that their equipment is correctly calibrated; and in 'proficiency testing', to ensure that their analyses are accurate (in which case, they would receive a 'blind' sample).

IRMM's will allow it to produce and characterise a wider range of materials.

"We will be able to produce very different materials from mixing dry powders, to filling liquids under conditions of low contamination," says professor Hendrick Emons, who heads the facility. IRMM produces a wide spectrum of reference materials, encompassing the steel, nuclear and medical industries as well as food. But it has recently expanded its activities in microbiology. It has developed a number of dedicated DNA fragments, to characterise both the "good guys" such as feed additives and the not-so-good-guys, such as E.coli.

It is also a recognised leader in reference materials for genetically modified organisms (GMOs), says Emons having developed the world's first such certified material back in 1999. "We have a continuous programme for GMOs," he says. "And it's not just for well-known species like soya: we're also working on cotton, potatoes and other products."

Reference materials do not have to be identical to one another there are often variations offered by several suppliers but this should not matter.

As a non-food example, Emons cites the case of sulphur levels in petrol. (There are strict legal limits on this.) Correctly prepared reference materials, of differing concentrations, should still lead to the same result allowing different laboratories to police rules accurately, he says.

Some of the new food-related materials that IRMM is working on include aflatoxins in pistachio nuts, and patulin a mycotoxin found in apples.

"We are also developing materials that are closer to the types of foods that consumers actually buy," says Emons.

Reference materials are usually supplied as dry powders, as this is the best way of stabilising the contents. But the drying process is quite destructive especially for things such as pesticides.

"Here, a more 'gentle' handling would be a big advantage," he says. "We're looking at the feasibility of producing these in the form of a wet paste. If we're optimistic, we could have the first commercial product ready in two to three years."

KEY CONTACTS​

Eurofins​ 0845 604 6740

IRMM​ 00 32 14 571 21

Wickham Laboratories​ 01329 832 511