Methanol an authenticity marker for Scotch whiskies

Researchers in Taiwan have shown in a preliminary study that levels of methanol may be used to distinguish adulterated and counterfeit Scotch whiskies from the genuine article.

Methanol is introduced in small amounts when distilled ethanol (EtOH) is used to falsify whisky, according to the scientists from Central Police University in Taoyuan City, who describe an analytical technique in the journal Forensic Science International that can detect methanol in samples down to 5 parts per million.

They bought 54 bottles of authentic single malt Scotch whiskies, 30 authentic blended whiskies and compared them with six adulterated samples seized by Taiwan police.

Detecting methanol can be considered an "exclusionary criterion" for the authentication of whiskies in Taiwan, they note – in other words, if it is present outside a normal range, the sample is more likely to adulterated or fake.

Four of the six adulterated samples were out of range, but two fell within it, "necessitating more complementary data to confirm their authenticity," according to the scientists.

Taiwan is a big market for Scotch whisky – importing £226m-worth in 2021 according to figures from the Scotch Whisky Association, which makes it the industry's third-largest export market.

Strong demand means that criminals follow the market, and according to the researchers tend to defraud consumers in one of two ways.

In the first, they take a small amount of premium-brand authentic whisky, mix it with rectified spirit (distilled ethanol) and flavours, and try to pass it off as a genuine brand at inflated prices.

The second is a lower-margin scam in which whisky is made almost entirely with rectified spirit and flavours, and sold as a lesser-known or even made-up brand.

Authentic whiskies have a tiny amount of methanol that is create during the fermentation process and not completely removed during distillation.

Producers have to meet strict level limits, as methanol can lead to blindness, nerve damage and even death if too much is consumed – which is the main factor behind the sometimes very high death tolls associated with fake liquor incidents.

Measuring methanol could be a "preceding eliminative marker for the rapid authentication of … seized bottled Scotch whiskies in Taiwan," according to the researchers.

Adulterated whiskies whose methanol concentrations lie within the normal range of authentic Scotch whiskies "need to be considered against more authentication criteria, such as the GC/MS analysis of other Scotch whisky congeners and isotope-ratio mass spectrometric analysis, etc".