Mineral and Isotopic Characterization of Wines From the Douro Demarcated Region

OBJECTIVES: In the 1960s, the French paradox launched the debate around the benefits of wine consumption. Since then several epidemiological studies have evidenced its potential protective cardiovascular effects. Wine's characteristics are highly dependent on the terroir. This study aims to characterize the profile of 11 minerals and micronutrients (K, Na, Ca, Fe, P, Mg, Mn, Se, Cu, Cr, and Zn) and the (87)Sr/(86)Sr isotopic ratio, and evaluate suitable tracers of authenticity for the Douro Demarcated Region. It will identify the parameters influenced by processing methods or environmental contamination and the ones common to the region, and fundamentally dependent on the soils and climate. METHODS: The sampling plan comprehended the collection of 15 Port wines and 15 Douro wines. All sample preparation occurred in cleanroom facilities, reagents were of high purity and Ultra-pure water grade I was used. Samples were mineralized using closed vessel microwave digestion. For isotopic analysis, a further purification step was required using Sr-selective resin Eichron®. Minerals and micronutrients were determined by inductively coupled plasma optical emission spectrometry (ICP-OES) and ICP-mass spectrometry (ICP-MS), and isotope ratios by multi collector-ICP-MS (MC-ICP-MS). ANOVA was applied to evaluate significant differences between the two types of wine. RESULTS: Results are within the maximum levels established by the International Organization of Vine and Wine (OIV), when applicable. k was the most abundant element in both types of wine with values ranging from 399 ± 7 to 1458 ± 7 mg/L. Se was the least abundant one presenting levels between the limit of quantification (2.5 μg/L) and 6.2 ± 0.2 μg/L. The statistical analysis showed significant differences between the two types of wine regarding six elements, namely Ca, Na, Zn, Cu, Cr, and Se. CONCLUSIONS: Six elements were identified as potential markers for the wines under study. Since all vineyards under study are grown in the same type of geological formation, the soil should not be responsible for these differences. Instead, they may result from agricultural practices, the winemaking process, or the aging of the wines. FUNDING SOURCES: This work was completed under the METROFOOD-PP project frame and received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 871083.