In August, US scientists announced that they had developed the first step on the way to producing portable detectors for a variety of nasty pathogens such as anthrax and smallpox, as well as food bugs.
Researchers in the biosecurity lab at the Lawrence Livermore National Laboratory said they had devised an array of gold and silver nanoscale wires to which they had attached antibodies for a particular pathogen. So when a pathogen was recognised and became biochemically bound to these antibodies, it produced a unique fluorescent striped pattern or 'barcode'.
Jeffrey Tok, principle researcher explains: "This produces a small, reliable, sensitive detection system that can be taken into the field." This all sounds very positive. However, unless the research can be commercialised and adapted to detect the bugs found in the food industry, food manufacturers will have to continue for the foreseeable future to rely on sending samples to testing laboratories to give their products the all-clear.
But food testing labs are doing their bit, too, and are developing new techniques to speed up and improve the reliability of microbiological and nutritional testing services.
Bodycote LawLabs, for instance, is applying DNA fingerprinting technology to microbiological testing for the food industry. It promises to give more certain results and speed up testing, says Liz Paterson, sales and marketing director of health sciences at Bodycote.
"We are using polymerase chain reaction (PCR). Basically, you take the DNA out of the cell in a sample, replicate it up and then look for a particular DNA sequence that characterises a particular bacteria. You can use it for Salmonella and Listeria and we are now looking to use it for legionella, which is quite difficult to detect."
The problem with microbiological testing for the food industry, says Paterson, is that labs are frequently asked to look for very low levels of contamination, as the recent Salmonella scare at Cadbury illustrated. A million Cadbury chocolate bars which may have been contaminated with a rare strain of Salmonella were recalled when a leading bacteriologist warned that the only safe level of Salmonella in chocolate was zero.
"You may be looking for one viable cell per organism in a sample of 25 grams," says Paterson. Also, if the product has been heat treated, any bacteria present may be lying dormant and must be resuscitated first with lots of food, water and oxygen before testing can begin.
"That is what takes the time. You have to grow the bacteria, culture it up, to a level where it is detectable, then differentiate it. And in some products, such as pizza which has got cheese on it, you have a natural bacterial loading already." That means you have to separate out the good bacteria from the bad, says Paterson, which means culturing up the bacteria on selective growing media. And it all takes time.
What PCR can do is give a much higher level of confidence in the results, says Paterson. But you still have to culture up the bacteria first. However, once that is done, PCR does reduce the time to get confirmation, she claims.
So far the main use for PCR in the food industry has been for detecting genetically modified organisms. It is still a long way from becoming a mainstream laboratory technique, says Paterson. The main reason is that the technology costs up to five times that of the traditional methods and yet may only save 12 hours. So there will only be a limited number of business situations where 12 hours can make a difference and where it's worth paying a premium for a PCR test, she suggests.
Another hurdle with PCR is that the technique has to be calibrated for each different food type. That may be all right for the meat industry or the dairy industry, says Paterson, where you have one type of food substrate such as raw meat or raw milk. "But we are taking in 900 samples a day over a huge range of food matrices, from finished meals to raw poultry and milk. So really, PCR will only be used where you have an investigation of a particular issue, or where the client wants a high level of confidence, or where speed really is of the essence."
Faster, more sensitive tests
There are increasing demands from the food industry and from the food safety authorities for faster, more sensitive tests and for greater confidence in the results. This means that it is now really only the larger, independent laboratory groups that can afford the equipment and technical back-up needed to develop new test procedures.
Bodycote, for example, has made a significant investment in combined liquid chromatography mass spectrometry equipment for hunting down pesticide residues. It can look for 200 compounds in one test, down to levels of parts per billion, says Paterson.
And the Eurofins group has recently invested in a high resolution combined gas chromatography mass spectrometry facility to speed up the detection and analysis of cancer-causing dioxins that are increasingly being found in the food chain.
Its newly opened laboratory in Hamburg can handle over 1,500 dioxin samples a month and has cut the time for testing for them from several weeks to 24-36 hours. The Hamburg laboratory is one of a number of Eurofins' centres of testing expertise or 'competence centres' across Europe.
According to Steve Revett, business development manager for food chemistry at Eurofins, many pan-European and multinational food manufacturers are increasingly looking to international laboratory groups like Eurofins for all their testing requirements. With the use of carriers like DHL, samples can now be delivered almost anywhere in Europe overnight.
The advantage, says Revett, is that food manufacturers get access to Eurofins' European network of laboratories and competence centres and its complete range of expertise simply by sending samples off to one designated Eurofins lab in each country.
"You don't have to split your sample and send a bit to this specialist lab or a bit to that specialist lab," says Revett.
Another benefit for the food manufacturer with factories in different countries is consistency of testing methods and results. "We put a lot of effort into ensuring we have consistency between our labs in different countries," says Revett.
But it isn't just concerns about bugs and bacteria that are keeping testing laboratories busy. The accelerating speed of new product development and the need to substantiate nutritional and health claims on food labels is also spurring laboratories to speed up and develop new methods of chemical analysis.
Functional foods
Reading Scientific Services (RSSL), for example, has recently created a new department dealing solely with functional foods and functional food ingredients. Jane Staniforth, head of food business development at RSSL, says the aim is to develop methods and tests to help food companies substantiate health and nutrition claims on food labelling.
"We are doing a lot of work on 'natural' foods, analysing the amount of polyphenols (antioxidants that may reduce the risk of cardiovascular disease), catechins (polyphenols found in green tea), isoflavones (another antioxidant), as well as minerals and vitamins.
"We can work closely with product developers on dosage levels and stability tests to make sure the active ingredient remains stable through the manufacturing and packaging processes and during the product's shelf-life."
Potentially it can be a long process, says Staniforth, which depends on the product. If it has a short shelf-life, then RSSL can get the data quickly and easily. But if a product has a 12 or 18 months shelf-life, it can be much more complicated, she says.
So in order to get products on to the supermarket shelves quickly, some food manufacturers take a belt and braces approach to nutrition labelling, says Staniforth. "They will take a flier and get some initial data. Then they will extend the shelf-life as more data comes through."
Another complication can be the way functional ingredients are now being added to a whole range of different foods. Take omega-3 fish oil as an example.
"We have had an analytical method for omega-3 for a number of years because it has been added in supplements for years," says Staniforth. "But once you start adding omega-3 to a food matrix, it makes it much harder to test it from an analytical point of view. New extraction methods need to be developed and worked through.
"So putting these ingredients in a cereal bar with lots of other ingredients, for example, or in a milk drink with stabilisers, can potentially affect the analysis. And clients don't always understand that," she adds. FM
Key Contacts
- Bodycote LawLabs 0121 251 4000
- Eurofins 08707 555 007
- RSSL 0800 243 482