A Toast to Authenticity

The proof is in the lighting

A single bottle of The Macallan 1926 recently fetched £2.1 million at auction, but even the world's most valuable whiskies are not immune to counterfeiters. As rare Scotch prices soar into the millions, scientists at the University of St Andrews have turned to quantum physics to authenticate what's inside these prized bottles — using Raman spectroscopy.

But how does light reveal what's inside a sealed bottle? Imagine throwing thousands of tiny rubber balls at a piano keyboard. Each key they hit would produce a unique note — some high, some low. Now picture a light beam doing something similar when it hits a liquid. The light particles, called photons, bounce off the molecules in the whisky like those rubber balls, and each molecule plays its own unique 'note' by changing the light's colour ever so slightly.

Just as every song has a unique combination of musical notes, every whisky creates a special pattern of scattered light. A genuine 25-year-old Macallan will 'play' a very different light symphony than a counterfeit trying to mimic it. The scientists' laser device acts like a music recorder, capturing these molecular melodies to reveal whether a whisky is authentic or fake — all without ever opening the bottle.

By detecting these tiny changes in the scattered light—some as small as one part in a million—scientists can map out molecular structures that were impossible to study a century ago. This phenomenon, discovered by physicist Chandrasekhara Venkata Raman, earned him the 1930 Nobel Prize and has become fundamental to modern chemical analysis.

Modern Raman devices use sensitive digital cameras and filters enabling portable kits to identify substances from pharmaceutical quality control to fine art conservation. However, there lies an issue with overcoming the challenge of scanning through glass. Just as the thick wall will muffle the music, the glass bottle’s molecular ‘notes’ can overwhelm the subtle ‘melody’ of the whisky inside. Dr Graham Bruce, Senior Research Laboratory Manager in the Optical Manipulation Group at the University of St Andrews, explains their innovative solution to this problem: "We shape the laser light into a ring on the glass bottle, and only collect light that comes back through the dark core of the ring. This way the light that comes back has to have come from within the bottle, rather than from the glass surface." Essentially, a little hole is drilled into the wall so that we can press our ears against it and discern the fine melody. 

The University of St Andrews’ team has built a portable Raman scanner to probe liquor samples. Their device shines an infrared laser at a droplet of the drink and analyses the scattered light using a compact spectrometer that fits in a small suitcase.

The researchers measured Raman spectra for many popular whisky brands, as well as vodka, rum, and other spirits. Each showed a distinct pattern of peaks corresponding to different molecules present. They then analysed spectra for confirmed fake alcohols supplied by trading standards teams and found obvious differences compared to the genuine samples.

The portable system can rapidly check a suspect bottle at the point of sale and immediately flag any fake drinks before they reach consumers. "The typical measurement time is around 5-10 seconds per bottle," notes Bruce, a significant improvement that enables quick testing without damaging stock or requiring lab analysis. The team is also examining options for further miniaturising the device so it can be easily used by retail staff and trading standards officers.

Raman spectroscopy provides a promising way to tackle alcohol counterfeiting. The approach is fast, non-destructive, and sensitive to subtle chemical differences between genuine and fake drinks.

Beyond the back bar shelves, Raman techniques have proven equally effective in identifying fake pharmaceuticals and tackling art forgery while physicists continue to advance the technology. With the global market for rare whiskies reaching record heights, this light-based authentication technology is not just protecting consumers and distillers — it is helping preserve the legacy of Scotland's most prestigious export. From auction houses to airport duty-free shops, these portable devices could soon become as essential to the whisky trade as the master distiller's nose — ensuring that what's in the bottle is as genuine as its price tag.

Illustration by Hannah Beggerow