The glittering prize
Could the use of gold help solve one of the whisky industry’s biggest challenges, to judge a spirit’s maturity without an expensive and time-consuming process? Tom Bruce-Gardyne investigates to find out how the precious metal could benefit the whisky world
When out of his white coat and lab goggles at the University of Glasgow’s School of Chemistry, Dr Will Peveler is fond of a dram. So, the chance to combine the two in some scientific analysis of whisky maturation was too good to miss. “The project started a year ago after talking to the Scotch Whisky Research Institute (SWRI) about some of the challenges and problems in whisky they were trying to solve,” he says.
For Will, cask ageing is “just that chemical exchange between spirit and wood. We were trying to quantify, in a broad way, how much that has happened, and how quickly.” Much like humans, the drink’s maturity cannot simply be measured in years.
ABOVE: Dr Will Peveler
ABOVE: Professor Alasdair Clark
There are myriad factors; from the age and size of the cask, to its previous contents, how often it’s been used, how it’s been charred, and so on. As he says: “These complex choices impact how much the new-make spirit draws from and reacts with the chemistry in the wood.”
His research paper, co-authored with Dr Jenny Gracie, may not have the catchiest title – ‘Growth of plasmonic nanoparticles for ageing cask-matured whisky’, but it does involve gold, tiny, precious fragments of the stuff. The metal was also used by his fellow university researcher and occasional collaborator, Professor Alasdair Clark, who developed ‘an artificial tongue’ for the drinks industry a few years ago.
Using a portable spectrometer and potentially an app on a smartphone, it is clearly a very practical device, compared with sending warehouse samples for analysis in a lab by “big ticket instruments”
Gold is exquisitely sensitive to its environment. “Little bits of gold sitting in the air look one colour, but if you put them in water, they’re a different colour because water has a different refractive index,” explains Alasdair.
Because these indexes vary among liquids, and even among whiskies, it enabled him to build a chequerboard of microscopic sensors akin to our tastebuds, and then measure how each one absorbs light when submerged.
It appears you can gauge maturity in a similar way. “We had this little test where the chemistry in the whisky was reacting with our gold salts, generating nanoparticles, and this gave us a bright red colour that we could measure in solution,” says Will. By noting the speed of the reaction, the intensity of the colour and the shape and size of the particles, a raft of different whiskies could be assessed and compared.
The device passed its first test, that of distinguishing Scotch from vodka, and then progressed to evaluate Tesco Special Reserve, Jura 10-year-old, Laphroaig and Highland Park among others.
ABOVE: diagram shows the process for detecting whisky maturation using rapid Au NP Syntheses (sourced via CC BY 4.0)
Highland Park was noted as producing ‘Au NPs with a very broad plasmon band and corresponding distinct grey colour’ – who knows, perhaps that’s a reaction to those long Orcadian winters? SWRI also provided benchmark samples that had been taken every six months from a single cask from day one to year six.
Using a portable spectrometer and potentially an app on a smartphone, it is clearly a very practical device, compared with sending warehouse samples for analysis in a lab by “big ticket instruments”, in Dr Will’s words, that work using gas chromatography. “This is hugely cheaper, faster and simpler,” he says. “This is something you could do in situ, and when we did a paper on how much it would cost, it came out at less than a penny to run each test.”
The attraction for the industry is obvious, although it does rather lack the romance of the master blender’s slow progression into the dark recesses of the warehouse, nosing every cask. Will is quick to stress that his machine is simply a diagnostic tool, with no pretensions to replace anyone. He would like to work with the Scotch whisky industry to develop this nanoparticle technique further. “Yes, we’re measuring total maturity, but there may be certain chemistry in there that will give certain flavour notes that we might be able to detect more specifically,” he says. “Maybe an estery banana note or a peaty smoky one?”
THE COST OF MATURITY
Maturity means time, and that costs money, which partly explains the removal of age statements from single malts, though it is a sensitive issue and there has been some kick-back from consumers. Numbers have sometimes disappeared from labels only to return, as happened with The Macallan a few years ago. Right now, Indian distillers are lobbying to be allowed to export their whisky as ‘whisky’ even if it’s less than three years old, as part of a UK trade deal. This longed-for deal may finally bring down import tariffs to the world’s biggest whisky market.
It is a tantalising prospect for Scottish distillers, although any quid pro quo on reducing the minimum maturation is not on the table. For the Scotch Whisky Association, three years and a day is a non-negotiable red line. Indian whisky-makers insist their whisky evaporates and matures much faster than Scotch, and that they need to bottle it before the angels take too much. “We urge the British side not to be unscientifically obstinate about it,” says Vinod Geri, head of the Indian distillers’ trade body, the CIABC.
For Dr Will: “It would be really interesting to test something that has been aged at a high temperature.”
Of course, how you define ‘maturity’ is ultimately subjective, and there are many aspects to how spirit evolves in the cask, as he explains: “There are a whole bunch of sequential chemical reactions that generate some of the final flavour molecules in whisky.” Maybe some of them can be speeded up, though with others you just have to wait.
The practical applications of this research can also evolve. Professor Alasdair Clark’s creation was billed as ‘the artificial tongue that could have whisky counterfeiting licked’. “That’s certainly one use,” he says, “but when we went to various beverage industries, they all came back saying we don’t lose as much money from fraud as we do from incorrectly brewing something.” Those microscopic slithers of gold could act as an early warning system before making a bad batch.
Yet preparing any invention for practical use is something else, as Alasdair explains: “When the world sees outputs from my lab or Will’s lab, what they don’t see are the years of banging our heads against a brick wall trying to make this technology, that hadn’t existed before, work for the first time. It’s one thing to have it work in my lab with a fair wind on a particular Tuesday when the stars are aligned. It’s very much another to have it work every single time.”
The practical applications of this research can also evolve. Professor Alasdair Clark’s creation was billed as ‘the artificial tongue that could have whisky counterfeiting licked’