How Do You Know A Rare Whisky Is Real? New Laser Light Technique Helps Identify Counterfeit Bottles

Even though the Covid-19 pandemic has brought economic uncertainty to many industries, one unlikely market has remained stable — rare whisky. Enthusiasts are still willing to shell out major money for exclusive bottles. Last month, a bottle of a rare Japanese whisky even set a new world auction record by selling for ten times the estimated sale.

And yet, while buyers are willing to spend up to and over a million dollars for the best of the best, tests conducted by the Scottish Universities Environmental Research Centre in late 2018 suggested that the risk of accidentally buying a counterfeit bottle is quite high. In fact, one third of the vintage Scotch whiskies tested in the study turned out to be frauds. Through analyzing samples from 55 bottles chosen at random from auctions, private collectors and retailers, the researchers determined that a whopping 21 were either not distilled in the year advertised, or were just outright fakes. 

A team of scientists from the School of Physics and Astronomy at the University of St Andrews have developed a new solution for whisky collectors who want to ensure their bottles are the real deal. And the best part is that the method doesn’t ever require opening the container. 

The research team’s recently published paper describes how they used laser spectroscopy to analyze whisky contents right through glass bottles.

Whiskies are chemically complex liquids which contain thousands of compounds that make up the distinct colors, aromas and flavors. Having a detailed understanding of the chemical composition of the bottle in front of you can be the difference between being certain a rare Scotch is what the label promises — or sniffing out a counterfeit.

Food scientists and chemists have previously investigated the use of spectrometers as tools to examine and identify the chemical compounds inside a whisky bottle. A spectrometer works by separating the spectral components of a material. Think of a prism which captures the light from the sun and separates it into a rainbow of colors. The light from a spectrometer will split the liquid into its component wavelengths. Then, the intensity of the light is measured to determine what compounds are inside.

The St Andrews researchers used laser spectroscopy, also known as Raman spectroscopy, a technique which uses laser light to separate the spectral components. When shone into a substance of interest, the laser induces a scattering of the various wavelengths. Researchers can then analyze the colors of the scattered light to identify the substance’s unique chemical fingerprint. 

However, while whisky producers and distributors have expressed an interest for “through-bottle” identification for years, glass is what scientists call “highly Raman active.” This means the glass bottle will produce a large spectral signal, which obscures the signals from the compounds in the liquid. So, in order to provide accurate analysis, scientists would have to remove a sample from the bottle before being able perform tests. 

Luckily, the St Andrews team developed a way to get around this major obstacle.

The researchers were successful in suppressing the signal from the glass by shaping the laser light into a ring, rather than using a standard beam. To create the ring-shaped laser light, the researchers used a special type of conical-shape lens called an axicon lens. The laser beam is then formed directly onto the glass wall of the bottle, which refocuses the light into the liquid and allows researchers to exclude signals from the glass in their analysis of the content.

This way, the whisky can stay in its original bottle all through testing, and not a single drop has to be wasted.

The researchers were also successful in using their technique to analyze bottles of gin and vodka. In the future, the relatively simple set up for the method could be easily produced and commercialized for widespread use.

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