SCIENTISTS are developing a new chemical fingerprinting approach to prove what winemakers and connoisseurs know by nose – Australian wines are distinct.
Knowing exactly what makes an Australian wine unique is going to be critical in combatting the growing problem of wine fraud, particularly when 50 per cent of Australian export wine is shipped in bulk and bottled overseas.
Working in collaboration with the Australian Wine Research Institute, CSIRO scientists are developing a chemical isotopic approach that can accurately fingerprint Australian wine so it can be distinguished from wine from other major wine producing countries and with the aim to protect the $2.22 billion wine export market from fraud.
Facing up to fraud
Before winemakers start to toy with grape juice, the sun, soil and water that go into growing the grapes make every drop unique.
However, wine fraud, although not new, is becoming increasingly more sophisticated, affecting wine markets around the world.
Perhaps the most high-profile case involved Rudy Kurniawan, the first person jailed for wine fraud after he was found substituting inexpensive Californian Napa Valley wine for high end French Burgundy in 2012.
Fraud is possible when it is difficult to prove the authenticity of wine.
"It’s very cheap to buy a low-cost wine or to blend wines from different origins and then put it into a bottle and print up any label you like,” says Dr Eric Wilkes, group manager at the Australian Wine Research Institute.
"Not only could the wine be fake and people inadvertently purchase a low quality fake wine, but they might even buy a contaminated product which creates a reputational risk.”
Picking the right trace elements
CSIRO principle research scientist Dr Jason Kirby says Europe has been developing sophisticated approaches for decades but until recently there hasn’t been need for a reliable method for authenticating Australian wine.
Determining the origin of wines using chemical markers depends on analysing parameters related to geology, water, environment and climate, as well as understanding the impacts of winemaking techniques.
The answer is in the chemistry, understanding the effects these various conditions have on the trace elements present in the wine. In particular, the isotopic makeup of certain elements present.
"The benefit of the isotope technique is it is a chemical fingerprint of the geographical location and environment in which the grapes are grown,” says Dr Kirby.
"Australia’s geology and climate are different to the rest of the world so we can use these unique chemical fingerprints to help identify authenticity.”
One technique is strontium isotope analysis, which has been used over the past ten years to test for geographic authenticity of foods including cheese, coffee, milk and orange juice.
"Strontium is very good at distinguishing between different types of groundwater so can be used to indicate the geographical region,” says Dr Wilkes.
Undoing the wine to find the isotopes
For CSIRO analytical chemist Claire Wright wine can be a “complex matrix that can contain a range of elements such as sodium, potassium, calcium, and magnesium and organic compounds at varying concentrations that can make accurate chemical and isotopic analysis challenging”.
In a recent study, the team analysed 231 Australian wines and compared them with 37 wines from bulk wine producing countries, using cabernet sauvignon and pinot noir for red wine, and chardonnay for white wine.
"Every sample has differing concentrations of elements but what we’re looking for is its unique isotopic signature. These variations that result from their environment and processing can provide a unique fingerprint of the origin of a bottle of wine,” Ms Wright says.
For isotopic analysis, the wine samples were evaporated to pre-concentrate elements and digested using strong acids to remove organic material. Using column purification chemistry, the element of interest, in this case strontium, is purified from potentially interfering matrix ions using ion exchange resins and acid elution procedures. The purified samples are analysed using a high resolution multicollector inductively coupled plasma-mass spectrometer (MC ICP-MS) instrument used to determine isotopic ratios with high precision and accuracy.
"Strontium is a really effective trace element for this analysis because there are high concentrations of this element in wines and it relates well to the geographical location and environment in which the grapes are grown,” Ms Wright says.
"There are a range of elements in wines currently being examined to provide a unique chemical fingerprint for Australian wines.”
The research team found that by assessing natural isotopic variations in elements such as strontium and trace metal concentrations it was possible to identify the origin of a bottle of wine.
Characterising Australian ‘terroir’
The team has recently included other elements in the Australian landscape into the model to refine their method for identifying geographic origin.
They have found it is possible to distinguish between major wine producing zones within Australia by analysing wine with strontium isotope ratios combined with a different set of trace elements (boron, barium, cobalt, lithium, manganese, nickel and rubidium).
"We are developing a capability so that wineries can do their own quality control checks,” Dr Wilkes says.
"It is a tool that can be used by industry to improve their confidence and manage reputation. The idea is it will be reasonably easy and low cost.”
The next step is expand the number and types of Australian wines analysed and compare them with wines from major global wine growing regions from around the world.
"We are confident that within two to three years we are going to have something robust,” says Dr Martin Day, chief investigator, Australian Wine Research Institute.
The research team is hoping to develop techniques to narrow down the origin of wines to a single vineyard. To ensure that the analytical parameters chosen are robust, wines will also be tracked over several years.
"Once we have develop a robust fingerprinting tool it will be available to the industry and community to differentiate wine from regions around the world and Australia and secure the quality and reputation of Australian wines,” says Dr Kirby.