isotopeFraud in the food and beverage industry and how applying isotope analysis technology can detect it is well documented, as my colleague Paul Dewsbury has noted in previous Analyte Guru blog posts.

As these earlier articles showed, food fraud often takes the form of labeling counterfeit goods as being from a particular, high value source or adulteration of premium foods with cheap additives. In this blog post, I’m going to look at probably the simplest form of adulteration, namely dilution of beverages with water and how studying isotope fingerprints in suspicious samples can identify fraudulent activity.

Wine is a particular target for fraudsters as it is a popular, large volume commodity, often associated with a high monetary value. Wine is commonly adulterated by the addition of fruit juices, water and sweeteners, which are not related to the grapes or fermentation process from which the wine was originally produced. The adulterated wine is then labelled and illegally sold as the original product (which is generally, as you would expect, an expensive brand). The integrity of wine is protected by various legislations around the world. In the European Union, for example, European Commission Regulation (EC) No 606/2009 regulates the origin and labeling of wine.

Outsmarting the Fraudsters

Food fraudsters may believe that addition of water to wine in relatively small amounts is undetectable, but unfortunately for them, it isn’t. The water contained in the original wine has a characteristic, a geographically specific oxygen isotope fingerprint, resulting from the isotope composition of the rain water taken up by the grape vines. Addition of water from another source changes this fingerprint sufficiently for isotope ratio mass spectrometers (IRMS’s), such as the EA IsoLink™ IRMS system, to detect the dilution.

Figure 1 below shows an example of wine adulteration by the addition of water, detected using oxygen isotope fingerprints. In this work, by my colleagues Jens Radke and Christopher Brodie, a genuine red wine sample was initially measured to provide a baseline oxygen isotope fingerprint before the sample was sequentially adulterated by adding water. Addition of water in this way reduces the alcohol content (which reduces the tax and customs duty imposed on exported wine in certain countries) and increases profits by facilitating the production of more bottles.

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Figure 1. Oxygen isotope fingerprints detect watering down of wine. (click to enlarge)

Figure 1 shows just how identifiable such adulteration is, although it has to be said that even the least discerning wine connoisseur might notice if the wine has been diluted by addition of an equal volume of water (i.e. 100% water added)!

Determining Origin Using Hydrogen and Oxygen Isotope Fingerprints

Isotope fingerprints are not only useful for detecting wine adulteration; they are also an effective means of determining the wine’s geographical origin. Differences in the extent of hydrogen and oxygen isotope fractionation in water during precipitation, evaporation or evapotranspiration result in wine samples carrying hydrogen and oxygen isotope fingerprints that are unique to a specific region (Figure 2). These subtle geographical differences provide powerful proof of the exact origin of wines suspected to have been fraudulently labelled.

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Figure 2. Changes in hydrogen and oxygen isotopes within the water cycle. (click to enlarge)

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You might be wondering how it’s possible for such small differences to really show where a particular wine has come from. Well, as you can see in Figure 3 below, the annual average of the δ18O values (the delta value is a means of expressing the ratio of a particular isotope pair in a sample relative to the same ratio in a certified isotope standard) varies noticeably across the world. By measuring multiple samples from a particular wine growing area using isotope ratio mass spectrometry, it can be possible to build up a clear, unambiguous isotope fingerprint allowing the integrity of wines from the region to be protected.

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Figure 3. Map showing oxygen isotopic fingerprints of water in precipitation* (click to enlarge)

The next time you enjoy a glass of your favourite wine, raise a toast to isotope ratio mass spectrometry for ensuring that what you’re drinking really is what is says on the bottle!

If you’re attending the Recent Advances in Food Analysis (RAFA) conference in Prague next month, drop by our booth (booth #8) and see what else we can do to meet your food analysis challenges. We’re also holding seminars at the conference on November 8th and November 9th where you can learn more about isotope fingerprinting and about various current food safety topics from users of our instruments.

Finally, if you’d like to learn more about using isotope fingerprinting to identify food fraud, visit our Investigating Authenticity and Tracing Origin with Isotope Fingerprints web page, and follow the Isotope Hunter on his quest to track the origin and history of your food and beverage products. For more information about applying isotope ratio mass spectrometry to fraud detection in other foodstuffs and beverages, take a look at our Food Authenticity and Labeling web pages and to browse application notes, scientific posters and webinars visit our dedicated food integrity webpage.

Thermo Scientific offers a wide range of other analytical solutions to help you achieve your food safety, authenticity and QA/QC objectives. If you have any questions about methods, workflows or products for these application areas, from trace elemental analysis and chromatography to organic elemental analysis and high resolution mass spectrometry, just let us know via the comments box below.

 

* From Bowen, G. Annu. Rev. Earth Planet. Sci. (2010), 161-187.