Mexican scientists develop reliable test for fake tequila

Scientists in Mexico say they have come up with what they say is a reliable test to distinguish high-value tequila from regular, lower quality variants.

By law, tequila must be made with Weber or Blue Weber varieties of the agave plant, with a minimum of 50 per cent of the alcohol content derived from agave sugars, although premium brands are made with 100 per cent.

Tequila can also only be produced in the Mexican states of Jalisco, Nayarit, Tamaulipas, Michoacan, and Guanajuato, and the sector is closely controlled by the Tequila Regulatory Council (CRT).

The top brands in the market – all 100% agave – are Don Julio, Ocho, Patrón, Calle 23 and Tapatio, according to 2019 figures from Drinks International. However, rising popularity and sales means that counterfeiters have started to focus on the category.

Writing in the journal Food Control, the Mexican research teams point to numerous cases in Mexico, the US and Europe where testing has revealed inauthentic tequila, often spiked with ethanol, methanol and other low-cost ingredients that in some cases pose serious health risks.

The scientists also cite studies suggesting 20 to 50 per cent of tequila sales are adulterated – equivalent to 60m litres of the liquor – which represents a n economic loss of around $550m.

In their study, they used an analytical procedure based on gas chromatography-isotope ratio mass spectrometry to detect stable isotopes of carbon and oxygen, combined with atomic absorption spectroscopy to measure copper content, in a range of tequila samples.

They compared samples that were based on 100 per cent sugars from the Agave tequilana Weber blue variety, with regular, lower-grade tequilas (51 per cent agave sugars) as well as some non-authentic beverages that had been seized by the CRT.

They found that a combination of the carbon 13 isotope ratio with the copper content was able to identify regular tequila and premium tequila “with a sensitivity of 100 per cent and a specificity of 100 per cent.”

Using the carbon ratio on its own wasn’t sensitive enough, they reported, and the oxygen ratio was less selective and could alter depending on environmental factors during agave cultivation and production.

“The method distinguishes tequila from other beverages produced from different agave plants (mezcal, raicilla and bacanora)” as well as those based on sugars from grape, corn, wheat and sugarcane, they concluded.