NZ-led research has wine industry fizzing

A new technique for analysing cloudy liquids being developed by researchers at Victoria University of Wellington has got the wine industry fizzing, and could be a game-changer in areas such as milk production, blood diagnostics and water quality monitoring, too.

Professor Eric Le Ru and two of his former PhD students, Dr Brendan Darby and Dr Matthias Meyer, from Victoria’s School of Chemical and Physical Sciences and the MacDiarmid Institute for Advanced Materials and Nanotechnology, have developed a technique for analysing turbid liquids (liquids that are opaque or murky) using absorption spectroscopy.

“The way light is scattered or absorbed by an object or substance reveals a wealth of information — our eyes are able to make use of this scattered light to detect the shape and colour of an object,” says Le Ru. “By shining lasers onto objects in a technique called Raman spectroscopy, the scattered light can provide a unique chemical fingerprint which can be used to identify many types of molecules.”

Le Ru and his research group are using nanoparticles of gold and silver to improve the sensitivity of these analytical methods.

“By using these metallic nanoparticles to boost the signal we get from these methods, we will be able to detect even the very smallest quantities — just one or two molecules of a substance. It’s the ultimate analytical tool.”

In the course of this fundamental research, the group developed new methods to characterise their samples using absorption spectroscopy, which is much more widely used by industries than Raman spectroscopy.

However, absorption spectroscopy can't be easily applied to murky solutions — the sample must be clear and transparent, which prevents it from being used to analyse liquids such as paint, milk, fruit juice, blood, seawater and industrial waste water. The same problem prevented them from measuring their gold and silver nanoparticles.

“The particles of turbid solutions scatter light all over the place, so when you send light through there’s not much coming out the other side and you can’t measure an absorption spectrum,” says Le Ru. “To measure it, you have to filter it to remove all the particles that are causing it to be cloudy, which takes time.”

However, over the course of several years, he and his colleagues have developed a way to measure the absorption spectrum of turbid liquids, which Le Ru believes could transform winemaking, healthcare and testing for pollution in waterways.

Le Ru and the team saw the commercial potential of their technique, and with the help of Victoria’s commercialisation office, VicLink, have developed a prototype with the working name of CloudSpec. The CloudSpec device has been put through some early field trials at a leading New Zealand wine company, showing promising results for improving wine colour measurement.

“We’ve got an instrument and we know it works, but now we’d like to build a more robust pre-production prototype that will be pretty much a final design. We’ve wanted to produce something that’s portable and which can be used on the spot — that might be a winemaker measuring the colour of their product, an environmental scientist testing pollution levels in a river, a medical technician testing blood in a laboratory or a farmer checking milk for certain residues in the dairy shed. It could potentially save those industries a lot of time and money.”

Le Ru says there’s also scope to extend the spectral range of their device to include UV light.

“At the moment, everything we do is in the visible range, so it would be really useful if we could analyse turbid solutions using UV light,” he says. “That would mean a huge ramp-up in how the device could be used — for example, it would allow wine and beer producers to monitor the alcoholic content of their product, and could also be used in water treatment plants as a way to kill bacteria more efficiently than current processes allow.”

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