Australian scientists have devised a way to uncover winemaking fraud following a study by experts from the Adelaide University and Australian Nuclear Science and Technology Organisation (ANSTO).
Team leader, Dr Graham Jones of the University of Adelaide's Department of Horticulture, Viticulture and Oenology collaborated with Dr Ewan Lawson and Dr Claudio Tuniz of ANSTO's Physics Division to authenticate samples of wine using radiocarbon dating.
Dr Jones said that the study showed that carbon dating the method better known for use on the Shroud of Turin and ancient relics such as rock art - can also be used for dating recent wine vintages.
"Detecting unauthorized additives and other wine forgeries is of growing importance to the industry," Dr Jones said.
The method relies on measuring the tiny amounts of Carbon 14 (14C) in materials which were once in equilibrium with the atmosphere. Incorporated within carbon dioxide, relatively large amounts of 14C were released as a result of atmospheric nuclear weapons testing during the 1950s and early 1960s.
The uptake of this atmospheric carbon dioxide by plants means that plant derived products can be accurately dated.
"The amounts of 14C to be found in plant material at particular dates are known from studies of tree rings and from atmospheric carbon dioxide samples," Dr Jones said.
"In the case of wine, sugars and other components such as flavour compounds accumulated in the grape berries during their ripening contain this age information. When the grapes are fermented into wine this information is retained in the alcohol and many other wine components."
Atmospheric radiocarbon levels surged after nuclear testing during the Cold War. During the bomb explosions the electrically neutral particles, neutrons, were generated which interacted with atmospheric nitrogen to form the carbon radioisotope.
Dr Jones said an interesting discovery as part of this research was that the amount of 14C in the southern hemisphere peaked a year or so after it peaked in the northern hemisphere.
Because Carbon 14 is found in one part for every trillion (one thousand billion) or less of other carbon isotopes, it requires extremely sensitive measurements.
These measurements were overseen by Dr Tuniz and Dr Lawson of ANSTO's Accelerator Mass Spectrometry group. AMS is an ultrasensitive analytical technique based on the use of an ion accelerator such as ANSTO's Australian National Tandem Accelerator for Applied Research (ANTARES).
Most of the measurements of the vintages coincided closely to their labelled dates. However the researchers are doing further work to check the results of one sample which showed a significant discrepancy with the vintage printed on the bottle.
Dr Jones notes that the proportion of Carbon 14 to ordinary carbon (carbon 12) in carbon dioxide in the atmosphere is declining to the point where the method may become unreliable in about the next 10 years unless more sensitive equipment is devised.
The study was partly funded by the Australian Institute of Nuclear Science and Engineering (AINSE) and the Australian Research Council (ARC). Mr Quan Hua and Dr Ugo Zoppi of the ANSTO AMS facility provided much of the technical support for this work.
Published: 17/10/2001