It is there to see in everything from broadband internet access to tilting trains -- the modern world is getting faster. In the food manufacturing sector, fast track techniques used in testing for microbes are now emerging (see page 48), but what scope is there for food companies to speed up other procedures in their labs?
For example, shelf-life testing is a complex process. If you want to know how a perishable product will age in a week, there's no real substitute for leaving it in a controlled environment for seven days. If, however, a manufacturer wants to know how a new chocolate bar will fare after several months at the back of a cupboard, accelerated shelf-life testing may seem an attractive proposition.
According to David Kilcast, head of business development for sensory science at Leatherhead Food International, extreme care must be taken when trying to speed up the ageing process: "You can only use acceleration in circumstances in which there's confidence that whatever factors limit the shelf-life under normal storage conditions can be speeded up. To get an accurate picture you need to accelerate only those changes and no others."
The basic message is that accelerated testing can only be used with confidence if the product is very well understood.
"The problem is that companies who are looking for accelerated testing are often producing new product types. They want a simple equation that says if it's like this after a week it'll be like that after a few months, but there are very few circumstances under which that can be done," says Kilcast.
Foods in which microbial growth is the limiting factor are likely to have short shelf-lives in any case, so acceleration will not be much of an issue.
Even so, Kilcast warns that altering the growth conditions of microbes, for example, by raising the temperature to accelerate other processes involved in product degradation, can sometimes have a disastrous effect on products that would be microbiologically stable under normal storage conditions.
"It's something you have to watch out for," he says.
Food manufacturers often use rules of thumb to allow them to estimate the shelf-life of new products from accelerated tests. For example, snack food manufacturers sometimes count one week at 37°C as equivalent to five weeks at ambient temperature.
There is also a general assumption that in microbiologically-stable foods containing oils or fats, rancidity will be the limiting factor, although Kilcast cautions that this is not universally the case.
Shelf-life prediction
Oils and fats become rancid through oxidation and many labs use Metrohm's Rancimat technology to speed the process up in a predictable way. Although the basic technique is well established, last year the company launched the 743 Rancimat, which offers computer control and can run up to 32 samples at eight different temperatures. Accumulating all this data at once has the potential to substantially speed up the process of predicting a shelf-life.
The technique works by blowing a stream of air through a heated sample, whose volatile oxidation products are transferred into a conductivity measuring vessel containing de-ionised water. While the sample remains stable the conductivity remains low, but as soon as it begins to oxidise, its volatile reaction products start to dissolve in the water and send the conductivity shooting up.
The period of time during which this happens is called the induction time and it's a reliable indicator of how stable the fats or oils in the sample are. The good thing about this approach is that the results can be extrapolated to give equivalent, longer induction times at lower temperatures.
Metrohm markets the Rancimat for quality control of oils and fats at the 'goods in' stage and for finished products, as well as for testing the effectiveness of antioxidants.
But Kilcast sounds another note of caution about using these kinds of tests for complex foods: "It's a very good approach for simple oils and fats but it may not be valid for some, more complex foods." But he adds: "It would be really useful, however, if a company wants to reformulate an existing product, for example, to make a healthier version by including oils with more polyunsaturates. Comparing the induction times of the old ingredients and the new ones would give a strong indication of relative shelf-life."
One type of product that is relatively well understood is chocolate and many confectionery companies routinely use different conditions of temperature and humidity to accelerate deterioration. Even so, Kilcast says things start to get complicated once the chocolate is used in more complex products: "Changes in the chocolate may be overtaken by changes in the other parts of the product."
For example, oil from the hazelnut in a praline centre could migrate to the surrounding chocolate, or the migration of moisture into a wafer may degrade a biscuit before there is a noticeable change in the chocolate coating.
"You have to have a real understanding of the product and how it changes with time," says Kilcast.
Chemical contaminants
Testing for chemical contaminants is another area of laboratory operations where speed can be of the essence. John Points, head of veterinary residues at analytical services provider LGC in Teddington, highlights two techniques that are making huge inroads into this field.
The first really comes into its own in relation to food scares. For example, when the Sudan I scandal broke, it was imperative for manufacturers to find out which products were affected as quickly as possible.
Sudan I is an oil-based industrial dye. Although it is not permitted in food, it was recently discovered after having been illegally added to chilli powder to enhance the spice's red colour. The problem was that when the first Sudan I incident happened in 2003, there was no routine test for the dye because it shouldn't have been in the food chain in the first place. It took weeks to develop and validate an effective test.
But when a similar scare cropped up in February 2005, analysts were ready to develop and validate an even more sensitive test, based on a technique that is speeding up testing for all kinds of contaminants. By combining liquid chromatography with mass spectrometry (a technique known as LC-MS) chemists can now devise tests to search for practically anything.
"If a food scare comes up we can now devise a test in days, rather than weeks or months," says Points. "Food scares are bound to keep happening, but the great thing about the new procedure is that it's so generic it's pretty much applicable to anything."
Because LC-MS is a combination of two different techniques, it is also especially good at distinguishing between compounds that are very similar in nature. For example, in the case of the first Sudan I scare, labs were initially trying to test for the dye using chromatography followed by ultra violet/visible light-based detection. But there are other compounds in chilli that tended to give false positives. Not only can LC-MS distinguish between all these compounds, it can even tell the difference between Sudan I and it's close chemical cousins, Sudan II, III and IV.
Shorter run time
As well as speeding up the development of new tests, LC-MS also reduces the run time taken for particular tests. "Because it's a lot more selective we don't have to get the chromatographic separation that we would have needed before," says Points. "It used to take hours but now it's just a couple of minutes."
He estimates that in terms of throughput, LC-MS enables labs to process five times as much in a batch as traditional techniques.
Although the equipment needed for LC-MS is expensive, Points says that it is gaining ground in in-house labs at the big food companies, as well as at the specialist contract labs.
Another technique whose development is so recent that it hasn't yet made much inroad into in-house labs is the combination of gas chromatography and time-of-flight mass spectrometry. According to Points, this approach is especially helpful when testing for pesticide residues and can reduce run times for tests from an hour to just five minutes. "But it's only really in the last year or two that the software has been developed to crunch all the data that this technique puts out," he says.
In terms of peripherals, such as lab management software, Points believes that the food companies are in a far better position to benefit than the contract labs.
"The scope for speeding things up through lab management, rather than new techniques, depends on the volume of work to be done," he says. "If a lab tests lots of similar samples then yes, it can really help. Contract labs such as LGC do lots of one-off tests and so there the scope for improvement is more limited." FM
Key contacts
- Leatherhead Food International 01372 376761
- LGC 020 8943 7000
- Metrohm 01280 824824