A team of scientists at the University of St Andrews has developed a laser spectroscopy technique that can determine the authenticity of expensive vintage whiskey without having to open the bottle to retrieve a sample for analysis.
Unless you stick to the bottom-shelf supermarket whiskeys, the question of authenticity can come with some very expensive answers. Not only can some bottles of famous vintage whiskeys fetch over a million dollars at auction, but cheaper bottles that "only" cost about US$100,000 are routinely bought to build up a collection as a financial investment. Additionally, ordinary retail spirits are counterfeited to such an extent that in Britain alone they result in revenue losses of £200 million (US$261 million) a year, so the question of whether the contents of a whiskey bottle matches the label can have a lot of money riding on the outcome.
For the vintage whiskeys, counterfeiters have become very adept at finding and reusing authentic bottles, labels, and stoppers to conceal the fact that the contents are nothing but flavored ethanol, so the only real way to be sure if the tipple is for real is to analyze the booze itself. We've covered numerous technologies developed to do just that, from artificial tongues that rely on "taste" to a portable device that analyzes the vapors given off by the liquor. The problem with all of these is that they involve opening the bottle to take a sample, which can destroy the monetary value of the item.
To overcome this, the St Andrews team from the School of Physics and Astronomy and led by Professor Kishan Dholakia have developed a new Raman laser spectroscopy technique that can determine the authenticity of whiskey without having to open the bottle or otherwise compromise it.
According to St Andrews, the idea of laser spectroscopy to authenticate wine and other substances isn't new but, until now, it's been hampered by the need to analyze the spirits directly. The reason is that Raman spectroscopy works by measuring how light scatters as it passes through and interacts with the sample's molecules to produce a unique signature. Unfortunately, the glass that makes up the bottle the whiskey is in also scatters the light, producing a strong signal that can swamp that of the contents.
The new technique avoids this by shooting two laser beams, one of which forms a ring of laser light on the bottle. Inside this ring, the second beam focuses on a specific spot inside the bottle's contents. This produces two signals from two different positions, so the detector can separate the glass signal from the whiskey signal.
"Personally, I hate it when I have to spare a drop of whiskey for validation checks," says Dholakia. "I’d much rather drink the whole bottle. Laser spectroscopy is a powerful tool for characterizing the chemical make-up of many materials, but to use it to characterize alcohol in its original container in this simple way is really exciting."
The research was published in Analytical Methods.
Source: University of St Andrews