Chemical characterization of tequila maturation process and their connection with the physicochemical properties of the cask

[Display omitted] •Tequila maturation was studied using isotopic, GC, FTIR and UV–vis analysis.•The pre-treatment of casks affects the rate of polyphenol extraction from the wood.•The evolution of polyphenol compounds can be described by Minchev & Minkov model.•Isotopic enrichment of δ18OVSMOW is related to polyphenolic compounds migration.•δ18O can be considered as an additional parameter for authenticity of aged tequila. The effect of time in the maturation process of Tequila employing two types of casks was studied: A new (labeled as Cask-New) and a medium-toasted cask (15 min at 200 °C) (labeled as Cask-MT). For that purpose, the wood used in the casks was characterized physicochemically, and its properties were contrasted with the physicochemical characterization of the beverage throughout the maturation time. To understand the kinetic maturation process, mathematical models were used. The best model that represented the polyphenol (I280) and flavonoid (I365) extraction was proposed by Minchev & Minkov. The extraction rate constants were: kcask-new,I280 = 0.233 month−1 vs. kCask-MT,I280 = 0.560 month−1, and kcask-new,I365 = 0.132 month-1 vs. kCask-MT,I365 = 0.383 month−1, explaining that the extraction process is slower in Cask-MT due to textural characteristics of casks, mainly related to the thermic treatment used in the toasting stage, which collapses the mesoporous structure having mass transfer limitations. The results obtained allow a better description of the maturation process, a fundamental step from a food engineering standpoint. The next step in the research should be to validate the proposed model to improve the final product quality.