GC-IRMS: Detecting purity and adulteration of tequila with isotope fingerprints

Product Manager
Sandra Forbes

Goal

Determine the purity of commercial tequila and detect adulteration.

Introduction

The blue agave (Agave tequilana Weber var. Azul), a plant indigenous to the Jalisco region in Mexico, is a significant economic product. Legally, it is the sole plant permitted for use in tequila production. Tequila is crafted from the fermented and distilled juices of A. tequilana. On a global scale, tequila is a well - liked alcoholic beverage, which has driven up demand and, consequently, production. This has led to a rise in its export value, benefiting the Mexican economy. Such popularity creates opportunities for economically motivated fraud, including the adulteration and mislabeling of authentic tequila or the production of counterfeit tequila.

Tequila generally falls into two main categories: pure tequila, which is 100% derived from A. tequilana, and mixed tequila, which contains A. tequilana with up to 49% sugarcane added. Tequila is safeguarded under the North American Free Trade Agreement (NAFTA) and local bilateral trade agreements. There are also regulations in place to combat fraudulent activities, such as the European Union Regulation (EC) 110/2008 (including its 2016 application related to tequila).

This application brief presents the carbon and oxygen measurements from commercial tequila, sugarcane, and the A. tequilana plant. These measurements were conducted using Gas Chromatography Isotope Ratio Mass Spectrometry. It also illustrates how isotope fingerprints can be utilized to detect beverage adulteration.

The isotope fingerprints of Agave tequilana and Mexican rainfall

In terms of photosynthesis, A. tequilana belongs to the CAM plant group, which means it has a well - characterized carbon isotope fingerprint ranging from - 12‰ to - 14‰[1]. During the growth of the plant, the biosynthesis of organic molecules in plants necessitates water, which mainly originates from rainfall (involving evaporation, sublimation, condensation, and precipitation in the water cycle). Tequila is produced solely in five regions of Mexico: Jalisco, Nayarit, Michoacan, Guanajuato, and Tamaulipas. This implies that the oxygen isotope fingerprint of the A. tequilana plant, as well as that of the local sugars used in mixed tequilas, is primarily determined by the rainfall water in these regions[2]. Consequently, it can serve as a geographical tool for determining the origin[3,4].

Is the tequila correctly labeled?

The data presented in Figure 1 display the measurements taken for mixed tequila, the A. tequilana plant, and pure sugarcane. The carbon and oxygen isotope fingerprint plot enables the distinction between the original branded mixed tequila and both the A. tequilana plant and sugar sources (such as corn and cane). This implies that mixed tequila can be clearly distinguished from pure tequila, which is sourced 100% from A. tequilana.

Moreover, the plot also highlights the disparities among A. tequilana, original mixed tequila, and sugar sources. This indicates that it is possible to differentiate adulterated and mislabeled tequila from authentic tequila and the original ingredients used in its production.

Figure 1. Carbon and oxygen isotope fingerprints of tequila.

Conclusions

The isotope fingerprints examined through GC - IRMS can effectively distinguish the purity of tequila and provide insights into adulteration and product mislabeling, thus supporting the regulations mentioned in the introduction. The GC IsoLink II IRMS System offers laboratories an efficient analytical approach centered on identifying isotope fingerprints in beverage samples. This system delivers rapid and reliable analyses with full automation.

References

1. Lopez, M.G. (2006) Authenticity: The case of Tequila In, Ebeler, S., Takeoka, G.R., Winterhalter, P. (eds.) Authentication of Food and Wine, pp. 273-287. American Chemical Society.

2. Hernandez-Antonio, A., et al. Hydrol. Earth Syst. Sci. 19. (2015), 3937-3950.

3. Augilar-Cisneros, B.O., Lopez, M.G., Richling, E., Heckel, F., Schreier, P. J. Agri. Food Chem. 50. (2002), 7520-7523.

4. Bauer-Christoph, C., Christoph, N., Aguilar-Cisneros, B.O., Lopez, M.G., Richling, E., Roassman, A., Schreier, P. Eur. Food Res. Technol. 217. (2003), 438-443.

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