Section 117(a) of the Federal Alcohol Administration Act ((27 U.S.C. 211(a)) defines “distilled spirits as ethyl alcohol, hydrated oxide of ethyl, spirits of wine, whiskey, rum, brandy, gin, and other distilled spirits, including all dilutions and mixtures thereof for nonindustrial use.” Distilled spirits, also known as hard liquor, is usually produced using a still where the components are separated from the mixture by using selective boiling and condensation. This process concentrates the liquid to produce beverages with a high alcohol content (typically 35-40%).
If you are a ‘manufacturer’ of distilled spirits, you need to make sure that the quality you expect from your product is the quality consumers find when they pour themselves a drink. UV-Visible spectroscopy has emerged as a powerful technique to test for authentication and adulteration of distilled spirits.
UV-Vis Spectroscopy
Several distilled spirits were analyzed using UV-Visible spectroscopy — a well-established analytical technique used in the food and beverage industry for research and testing in the quality control stage.
UV-Visible spectroscopy measures the absorption or reflectance of light in the ultraviolet and /or visible region of the spectrum. In the most basic terms, spectrophotometers enable photometric comparisons of relative light intensities across the ultraviolet and visible spectrums. Directing a controlled, constant intensity light source (halogen, deuterium, or xenon) across the spectrum or at a specific wavelength through a sample easily can confirm known or calculate unknown characteristics of the sample. The incident light (I0) can be redirected backward as reflection, suffer an energy loss as absorption, and pass through transparent or translucent samples as transmission. (Read more about UV-Vis spectrophotometers.)
The Challenge of Counterfeiting and Adulteration
Whiskey is a premium spirit beverage that is distilled using a complex aging process. It is produced by mixing various grains with water to form a mash that is fermented with yeast, and then distilled to generate an alcoholic distillate, and finally matured in wooden barrels or casks.1 This is a complex and traditional process that results in a beverage that has both a high value and high degree of variability. Because whiskey usually has a high retail price, counterfeiting and/or adulteration is common – which could be dangerous because there are no controls over how much or which chemicals or cheaper alcohols are added to the mix.
There are consequences under the FAA Act if a determination is found that an alcohol beverage product is adulterated. According to the US Alcohol and Tobacco Tax and Trade Bureau (TTB),
“The sale or shipment of an adulterated alcohol beverage in interstate or foreign commerce by an industry member subject to the provisions of 27 U.S.C. 205(e) constitutes a violation of the FAA Act, even if the bottler or importer of the product in question has obtained a certificate of label approval (COLA) or an approved formula….
“Subject to the jurisdictional requirements of the FAA Act, mislabeled distilled spirits, wines, and malt beverages, including adulterated products, may not be sold or shipped, delivered for sale or shipment, or otherwise introduced or received in interstate or foreign commerce, or removed from customs custody for consumption, by a producer, importer, or wholesaler, or other industry member subject to 27 U.S.C. 205(e). TTB may pursue action to suspend or to revoke the FAA Act basic permit of industry members who willfully violate the conditions of their permit with respect to mislabeled, adulterated products. See 27 U.S.C. 204(e). Violations of the labeling provisions of the FAA Act are punishable as misdemeanors and the Government may seek injunctive relief to prevent and restrain such violations.”
Whiskey Analysis
Three different whiskey samples were analyzed using a UV-Vis spectrophotometer. Whiskeys have unique UV-Vis absorption spectra that depend on their composition and age. Below are the UV-Vis spectra of various whiskeys.
Note specifically the absorption features present in the deep UV region. Spirit Caramel is known to absorb in the deep UV region. Spirit Caramel refers to high molecular weight, brown compounds that are formed when sugar (sucrose or glucose) is heated in the presence of certain tanning accelerators. Most Scotch, and many Irish whiskies are colored with the addition of E150A food coloring (commonly known as spirit caramel).3 This coloring is used for cosmetic reasons as sometimes the casks and barrels used in the whiskey-making process may impart different coloring into the liquid based on the age of the wood and how many times it’s been used. Darker whiskeys also give the impression that they are older than they are, so some consumers think it is deceptive. The practice is limited, however, and many countries prohibit the use of spirit caramel.
Based on industry literature, many groups have used full spectral data to develop powerful chemometric models that are able to discriminate whiskey brands and detect adulteration. For examples, an article published in the journal “Food Chemistry” addresses the ability to use multivariate data analysis to discriminate between counterfeit whiskies and the authentic brand. 2 Another group has used UV-Vis spectroscopy in conjunction with other analytical techniques to develop methods for discriminating between whiskies produced in different regions (Scotland, Spain, US, and Ireland).4
You can get more details about the analyses, parameters, and instruments used for this experiment and others in the food and beverage industry by watching the webinar: UV-Vis Spectroscopy Techniques in Food and Beverage Analysis.
Summary
UV-Vis spectroscopy is a powerful analytical technique that gives quantitative information about chemical analytes in a sample. It has been widely adopted across food and beverage industries, including in the manufacture of spirits, because it requires minimal or no sample preparation, is a low-cost analytical technique, and excels in applications that range from composition, quality, authentication, and adulteration.
In other words, it’s not so scary to use.
Additional Resources and References
- Webinar: UV-Vis Spectroscopy Techniques in Food and Beverage Analysis.
- Find more information on food & beverage analysis
- UV-Vis instruments
- Join the Materials Research Community
- Poisson, L & Schieberle, P. Characterization of the most odor-active compounds in an American bourbon whisky by application of the aroma extract dilution analysis. Journal of Agricultural and Food Chemistry. 2008, 56, 5813-5819.
- Martins AR, Talhavini M, Vieira ML, Zacca JJ, & Braga JW. Discrimination of whisky brands and counterfeit identification by UV-Vis spectroscopy and multivariate data analysis. Food Chem. 2017, 229, 142-151.
- Whiskipedia (https://whiskipedia.com/fundamentals/spirit-caramel/)
- Wiśniewska, P., Boqué, R., Borràs, E., Busto, O., Wardencki, W., Namieśnik, J., & Dymerski, T. Authentication of whisky due to its botanical origin and way of production by instrumental analysis and multivariate classification methods. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 2017, 173, 849-853.
