Development of tools to verify origin and varietal nature of wines
Origin verification of wines relies on the use of parameters that not only reflect the geology and water source of the location where grapes are grown, but which are also not altered during vinification. Building on a recently completed AWRI feasibility study, several additional elemental isotope ratios such as boron, lithium and lead are now being measured as part of the Wine Australia project AWR1505, in order to provide information additional to the strontium isotope ratio, on the crustal composition of source vineyard location.
To supplement this dataset of trace elements and their isotopes, and to achieve true independence of multiple data sources, oxygen-18 will also be analysed as an indication of the vineyard water source. These parameters will be measured in a large number of Australian wines, and wines from North and South America, Europe, and mainland Asia and Africa.
In order to verify that chosen parameters are not affected by variety (as has been highlighted in several recent papers in the literature), laboratory-scale wines will be made to assess numerous varieties grown in the same soil across several different locations. In addition, the temporal variation of these parameters will be assessed through the analysis of several vertical series of wines made from single vineyards over the last ten years. This information will be combined with the continued survey of the parameters determined to be most robust over a five-year period, to provide a series of reliable analytical protocols and metrics for the determination of wine origin.
In the later years of the project, a review of chemical and genetic techniques for the determination of varietal origin of wine will be undertaken, with the aim of targeting appropriate tools for this aspect of wine authentication.
Identifying wine provenance
This project is in its final phase with the focus on completing the analysis of the data acquired, developing recommendations for industry and preparing results for publication. The project has successfully identified a combination of isotopic ratios that can be used to give a good indication if a wine is of Australian origin and provide pointers to the possible region within Australia it may have originated from. The methodology developed does not give a simple in-market method to absolutely determine if an unknown wine is Australian. In fact, the research suggests that doing this with 100% confidence is unlikely without significant technology development and massively increased commitment to databases of isotopic ratios in wine, which was not the aim of the project. Instead, the method developed provides an important tool that can be used when provenance disputes arise in legal or regulatory environments.
The project has also identified the weaknesses of some elemental and isotopic tools currently in use for the assessment of wine provenance internationally. These include the impact of bentonite fining on the use of trace elemental or lead isotope analysis to identify the origin of white wines and some of the weaknesses of oxygen isotope ratios in accurately determining the addition of water to must and wine. A further outcome has been a clear understanding of the impact of the origin of glass wine bottles on the use of isotopic measurements for provenance, in particular the use of boron isotopes. While the current research project on the use of isotopic measurement for identifying provenance is winding up, the AWRI’s involvement in the area will continue through a range of collaborations and some commercial activities.