Isotopic differences between Tequila and Tequila 100% agave silver class: Effect of sugar enrichment on the ¹³C_VPDB on the beverage congeners

According to the Official Mexican Standard NOM-006-SCFI-2012, Tequila has two categories: "Tequila 100% agave" and "Tequila". Unlike Tequila 100% agave, the Tequila category can be enriched with other sugars different from Agave tequilana Weber blue variety up to a proportion no greater than 49% units of mass. At the moment there are numerous scientific reports where the Tequila 100% agave category has been isotopically characterized, however, there is still a need to study the Tequila category in order to obtain fundamental information useful to strengthen the inspection processes of the beverage to guarantee its authenticity and quality. Due to the above, this research work shows the isotopic characterization of delta C-13(VPDB) values in congeners in Tequila silver class samples (n=25) and Tequila 100% agave silver class samples (n=69) to determine isotopic differences between categories. The characterization was complemented by determining the delta O-18(VSMOW) for the ethanol molecule. The results obtained show that there are no statistically significant differences for methanol (p-value 0.09>0.05), n-propanol (p-value 0.31>0.05), isobutanol (p-value 0.07>0.05), isoamyl alcohol (p-value 0.17 >0.05), and ethanol (p-value 0.93>0.05). On the other hand, for acetaldehyde (p-value 0.00<0.05) there are statistically significant differences. The observed differences correspond to more positive delta C-13(VPDB) values for the Tequila category related to the fact that during the fermentation stage these compounds are produced from a mixture of raw materials (51% Agave tequilana Weber blue variety and 49% sugars such as sucrose, dextrose or Frudex (R); sugar sources coming mainly from plants with C4 metabolism). The results obtained show fundamental information useful as an additional criterion from the parameters already established in the Official Mexican Standard NOM-006-SCFI-2012 to differentiate both categories of Tequila.