wine analysis methodsMy colleague Paul Dewsbury has gotten me thinking a lot about wine fraud lately. Occasionally, I like to put on a blind wine tasting party for my friends in which I disguise several bottles of wine that cover the range from cheap to expensive and have everyone taste them all with me and record our impressions.

It’s fun for me to see if I actually do like that expensive bottle of wine I keep pulling out for special occasions, or if a bottle at half the price would please me just as well or even more. It’s always interesting to observe the vastly different reactions different people can have to the same wine.

The wine industry may sometimes disagree but really wine is a subjective thing: what some people love, others will hate. Maybe, that’s part of how wine fraudsters can get away with marketing fraudulent wine. Most people can’t tell if a wine is truly what it’s labeled to be, or if it’s a cheaper alternative.

 

Multiple Wine Fraud Mechanisms

Most of what I know about wine fraud involves simply labeling a cheaper wine as a more expensive one. There’s even a new wine fraud website in the works to help people identify if their wine is authentic. But as I stared at my friends’ purple smiles at my party, I began to wonder if added substances like illegal dyes sometimes make it in to fraudulent wines also. It turns out, unfortunately, the answer may be yes.

Some wine fraud takes the form of serious chemical adulteration. Wine can be tainted with methyl alcohol to raise the alcohol content, with diethylene glycol to make the wine sweeter, and so on and so forth. What if after this adulteration, the wine is off color? Wine adulteration with colorings – many of which might be illegal to use in food products – then becomes a concern.

 

QuEChERS and LCMS Detection of Illegal Dyes in Wine

So, how might one detect these unwanted and potentially dangerous colorings? In my research, I came across a recently published mass spectrometry method from scientists at the Shaanxi University of Science and Technology, the Chinese Academy of Inspection and Quarantine, and the Beijing Entry-Exit Inspection and Quarantine Bureau in collaboration with one of my colleagues here at Thermo Fisher Scientific Inc.

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In their paper, titled Simultaneous Determination of Dyes in Wines by HPLC Coupled to Quadrupole Orbitrap Mass Spectrometry (link to article abstract), the researchers explain how they developed a sample preparation, separation, and detection method to screen for 69 different dyes in wine. Sample preparation was done via a simple QuEChERS method. Acetonitrile, ethyl acetate, and acetone extractions were tested and the researchers found that acetonitrile provided better extraction efficiency for all of the analytes, while acetone was the worst.

An acetate-buffered method was used to improve stability and recovery of pH-dependent compounds. The sample preparation method was examined in great detail – I highly recommend you take a look at the paper. For separation, three liquid chromatography columns were tested and the solid-core polar endcapped HPLC column (Thermo Scientific Accucore aQ C18 Polar Endcapped LC Column) provided the best resolution.

For separation and detection, the researchers used one of our mass spectrometers (Thermo Scientific Q Exactive Quadrupole-Orbitrap MS system) coupled to one of our HPLC systems (Thermo Scientific Accela HPLC system). Recoveries ranged from 87.2 – 107.4% with coefficient of variation less than 6.4%. The method is the first method I’ve seen for multiclass determination of so many dyes.

 

Additional Resources

We also have some additional resources that I’d like to point you to if you’re interested in detection of dyes, wine analysis methods, or food adulteration analysis.

 

Are wine analysis methods of interest to your laboratory? If so I would like to hear your thoughts and experiences.