Identifying Whiskey Counterfeits

Strong differentiators between the whiskies in negative ion mode identified include capric and lauric acids. These acids derive from barley lipids and remain in the whisky after alembic distillation from copper pots. They are detected at higher levels in Scotch whiskies. Another strong differentiator for Canadian whisky was identified as containing sulfur (by mass and isotopic pattern), which may relate to the caramel that is legally added to these blends. Another clear marker, ellagic acid, is the end product of the degradation of barley tannins and also present in oak wood; and is detected at high levels in certain Scotch whiskies. So a number of markers has clearly been detected and identified for the various whiskies tested using negative ion mode LC/MS, however complete separation of all samples studied was not able to be obtained.

Data Fusion

Review of the same parameters for positive ion mode LC/MS also revealed markers that helped to distinguish between the Canadian blends and Scotch whiskies. But like the LC/MS results in negative mode, it failed to distinguish between two Scotch blend samples. How can this issue be resolved and allow for an unambiguous result to help confirm authenticity? By fusing data from orthogonal analytical techniques, LC/MS and ICP-MS, there’s an opportunity to develop truly unique product profiles. By fusing together the inorganic and organic markers into one table enabled a complete separation of all of the whisky groups, see Figure 3.

Image Credit: PerkinElmer
Figure 4: Attenuated total reflectance.

The LC/MS and ICP-MS analyses detected chemicals and elements related to the wood, maturation, and distillation methods used in whisky production. It’s only when using data fusion (combining results from independent analyses on the same samples) that a more complete differentiation of blends was produced. This output reveals characteristic markers that aid determination of the origin of different whiskies. And similar analysis could be used to assign the geographical origins of unknown whiskies and to highlight adulterated and fraudulent samples.

Rapid Screening Methodologies

It’s been shown how sophisticated analytical techniques can be employed to generate unique profiles that can be used as markers for origin and authenticity. Whilst providing very insightful data and analysis, such methodologies do not lend themselves to swift screening. Molecular spectroscopic-based technologies are particularly well suited to rapid screening testing. They are relatively inexpensive, easy to operate, and give a fast answer.

Using IR Spectroscopy

Whisky samples have been studied by both mid- and near-infrared (IR) spectroscopy. There are also a number of different sampling techniques that can be employed when collecting IR measurements. One of the fastest and certainly most convenient for real-time analysis of whisky samples is by attenuated total reflectance (ATR) (see Figure 4).

Image Credit: PerkinElmer
Figure 5: ATR spectra of whisky (top), ethanol (middle), and water (bottom).

In ATR, the sample is placed on top of a suitable crystal material. The IR beam passes through the crystal, which then penetrates a small distance into the sample before it is reflected back in to the crystal and to the IR detector, generating an IR spectrum. Due to the strong absorptions present in mid-IR, ATR can be applied successfully.

Figure 5 on page 41 shows the ATR spectra for a whisky sample, ethanol, and water. Since water and ethanol are the major ingredients in whisky, it is dominated by their spectral features. The mid-IR region of the spectrum is obscured by the very strongly absorbing bands for water (in the approximate regions of 1,640 cm-1 and 3,400 cm-1). The weaker bands in the near-IR region of the spectrum are much more suitable for the analysis of such aqueous based samples; in this region, it is possible to observe the combination bands for water (at 5,167 cm-1) and ethanol (in the region 4,420 cm-1 to 4,300 cm-1).