Research team develops whisky characterisation technique

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A team at the physics department at St Andrews University has developed a microfluidic device to detect counterfeit whisky samples. Praveen Ashok, Kishan Dholakia and Bavishna Praveen of the optical manipulation group used Near Infrared (NIR) spectroscopy to analyse 20µl samples of commercially available single malt whiskies to not only detect counterfeits, but also characterise genuine samples by brand, age and even cask.

A whisky’s distinctive flavour, which is determined by its congener profile, is very difficult to mimic. This profile is governed by organic compounds formed during fermentation and during maturation in wooden casks. Amounting to less than 1 per cent of the total volume, these include organic acids, higher order alcohols, esters, and aldehydes and wood extracts, such as tannin, acid and colouring matters.

Raman and fluorescence spectra were recorded from the sample by an Andor Shamrock SR-303i spectrometer equipped with an Andor Newton DU920P BR-DD back-illuminated, thermoelectrically-cooled CCD camera.

'The Raman spectra of the whisky samples is dominated by peaks corresponding to 40 per cent ethanol and our results clearly demonstrate that the alcohol content may be predicted to a probability of more than 99 per cent, enough to rapidly weed out the majority of fakes,' said Ashok. 'Although the congener components could not be distinguished from differences in the Raman peaks, the broad fluorescence background is markedly different for different types of whisky due to the variation in congener profiles. The result is successful classification of whiskies based upon their age, origin and cask – a skill few human palettes can match.

'We chose the Andor analytical instruments due to the high sensitivity of the DU920P BR-DD CCD camera and the small form factor of the Shamrock SR-303i spectrometer. While its performance is every bit as good as a bench-top system, the Shamrock’s compact size and low weight lent it a degree of portability as well. This was important to us as we wanted to demonstrate the potential of a hand-held device that could be used by distilleries to quality control their production by benchmarking against a known standard. The same hand-held instrument could also be used to test for counterfeit whisky bottles and confidently deliver reliable results in seconds,' concluded Ashok.

Andor’s modular spectroscopy solutions encompass a wide range of high performance CCD, ICCD, EMCCD and InGaAs array detectors, as well as a comprehensive range of research-grade spectrograph platforms.

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