Up close and personal with near infrared

There is no denying that science is getting more popular, and perhaps even sexier. Just take a look at the success of TV show, The Big Bang Theory, or how many times Professor Stephen Hawkings has appeared on The Simpsons. (It’s five, and he’s been mentioned another two times.) But the near infrared spectroscopy (NIRS) community are concerned they might be getting left behind.

At NIR 2011, the 15th international conference on NIRS, held in Cape Town in May this year, the community gathered to discuss ways to popularise their field. On face value, it appears that NIR is playing second fiddle to related technologies such as microwaves and x-rays, both household names thanks to applications that people encounter in their daily lives.  Digging a bit deeper, there are however some pretty interesting applications of NIR that could raise awareness of the field and be the key to popularising the technology. As Professor Heinz Siesler of the University of Duisberg-Essen said: ‘We don’t know how to communicate in a popular way and transfer knowledge on a more popular basis.’

It turns out that NIRS is fairly widely used in South Africa, from studying fossils, to measuring the alcohol and sugar content in wine, protein, fat and moisture during the food production process.

Dr Marena Manley, of the Food Science Department at the University of Stellenbosch, is on a drive to increase local uptake of the technology and also adapt the implementation to better suit local requirements.

‘While NIR technology is used in South Africa, we are lagging behind in terms of research to find optimal applications for unique South African products and conditions,’ she said. ‘We also need to develop more people with skills who are able to correctly calibrate NIR instrumentation for specific, local needs.’

NIRS has some compelling advantages over previous wet chemical processes used for food testing: it does not require harsh chemicals so is safer, quicker, cheaper and has less of an impact on the environment. Several constituents can be measured at the same time, further saving time. The process does not harm or destroy the item being tested, and can easily be implemented during the production process, allowing manufacturers to correct errors on the fly, rather than having entire batches being spoiled.

Ongoing checking during production also means that producers can be confident about the quality of their entire output because all items are checked, rather than merely a sample.

‘Because you can measure the entire spectrum, NIRS gives you a fingerprint of the entire sample, not just one parameter,’ said Manley.

It appears that if the equipment is correctly calibrated, and the sample correctly handled, accurate results can be achieved relatively easily – with the push of a button. The tests can even be run remotely, ethernet access to NIR spectrometers allow for remote control and diagnostics via a company intranet or the internet – truly processing in the dark, said Tony Blakeney from Australia’s Cereal Solutions.

Manley maintained that the initial investment in equipment and specialised skills to calibrate the instrumentation is recovered within three to five years. On the skills development front, Manley said that between virtual learning, visiting international trainers, or students studying abroad, the required skills are being created locally.

Low levels

Despite the benefits mentioned above, and the ease of use, it does appear that NIRS has some limitations and struggles with low levels, said Manley. In addition, NIRS can’t measure minerals but can measure the changes they cause.

NIRS has applications in the entire food production process, from measuring protein, fat or moisture in raw materials, such as wheat, rice or milk; through to the testing of constituent elements and their combination; to testing a final product to verify quality, origin, ripeness and that the product is what it says it is.

Although it is still early days, a discussion around miniaturisation showed the potential for NIR to enter our daily lives, particularly with regards to food consumption. Personal NIRS devices could help people with food intolerances – such as lactose and gluten – determine which food is safe for them to eat. Professor Hideo Itozaki, from Osaka University is exploring how NIRS can be used to scan water and other liquids at airports to uncover explosives (and to save the rest of us from having to buy expensive airport water once we are through customs!)

The technology itself has only been commercially implemented for less than 30 years, with the first commercial NIR spectroscope being deployed in 1972 in the Canadian wheat industry. As well as the food industry, NIR is being used in space exploration, the pharmaceutical industry and agriculture amongst others. The future could hold a device that measures the exact mix of petrol in your car and adjusts your engine to improve fuel efficiency, fridges that tell you which if your food has gone bad, and three-dimensional imaging for greater visibility over what you are measuring.

NIRS basics

NIR = near infrared. This refers to electromagnetic radiation with a wavelength longer than visible light, so to the human eye, located just adjacent to red in the spectrum. Infrared is divided into three bands, with NIR being the closest to visible light, between around 0.7 micrometres and 300 micrometres (there is no hard and fast rule on the ranges).

NIRS – Near infrared spectroscopy. Using NIR as a measurement tool.

How NIRS works

A beam of infrared light is passed through a sample, which could be gas, liquid or solid, or a combination of states, for instance yoghurt with chocolate chips. Once the light beam passes through the sample it is examined to see how much of it was absorbed or transmitted, and which wavelengths were absorbed or transmitted. Each chemical bond vibrates at a characteristic frequency, and most of these frequencies correspond to a frequency of infrared light. Where the frequencies match the light is absorbed. So an analysis of the light absorbed or transmitted tells you about the composition of the sample.

Typically a NIR spectroscope would be carefully calibrated according to how it was going to be used, and the results analysed accordingly.

First published on South African Food Review.

 

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