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Beer Tongue

February 10, 2014

I enjoy beer, although my annual consumption is far less than the 78 liter per capita average for the United States. I need to limit my beer consumption, so that these blog articles remain comprehensible; or, at least, less incomprehensible. More than 24 billion liters of beer are consumed in the US each year, so beer is big business.

The legal drinking age was eighteen when I was in college in the 1960s. This wasn't a good idea, and that's why the age has been raised to twenty-one. This was a time long before today's microbrew culture, so there wasn't much of a choice of what to drink.

One interesting thing we would do in those days was to buy an assortment of lesser known beers from a beer distributor. The distributor likely got small quantities of these gratis from companies hoping to get brand recognition. With this stock, we would have a beer tasting party to rank these in order of preference.

One thing we learned at these parties is that different people enjoy different tastes. This was an example of the Latin maxim, "De gustibus non disputandum est" ("About taste there can be no argument"). Nowadays, my favorite beer is Heineken (from glass bottles, only), but I'm sure there are many who don't like Heineken.

Beer is very easy to make. Cereal was first farmed about 11,000 years ago, in the early Neolithic period, and it's thought that the first beer was produced shortly thereafter. Beer production, or brewing, simply involves steeping cereal grains in water, then fermenting the mixture with yeast.

The brewing process may be simple, but the beer product contains a complex mixture of chemicals, most of which are listed below.[1]

Ethanolb-Phenylethyl acetate
Ethyl acetateb-Phenylethyl acetate isomer
Isopropyl acetateCapric acid
Ethyl propionateEthyl caprate
1-PentanolEthyl 4-decenoate
2-Methyl-1-butanolp-Vinylguaiacol
Ethyl butyrateMonoterpenes
Isopentyl acetateEthyl hydrocinnamate
Ethyl caproateb-Damascenone
Isooctanolc-Nonalactone
1-Octanolb-Phenylethyl butyrate
LinaloolButylated hydroxytoluene
Caprylic acidEthyl laurate
C8 acidsNerolidol
C8 estersEthyl cinnamate
Ethyl caprylateCaryophyllenyl alcohol
b-Phenylethyl alcoholOxygenated sesquiterpenes
Benzoic acids-Cadinene
Ethyl benzoateb-Cadinene
1-UndecanolCaryophyllene oxide
cis-geraniolDibutyl phthalate
Aromatic acids

Structure of Geraniol

Geraniol (C10H18O), a chemical found in beer, is a flavoring compound in many fruits. Carbon = black, hydrogen = white, and oxygen = red. (Illustration by Jynto and Ben Mills, via Wikimedia Commons.)


A beer will taste the way that it does because of the relative amounts of the chemical constituents that it contains. An analytical chemistry laboratory would be able to sort the Heineken from the Miller Lite, but only after considerable time and expense. A device capable of doing inexpensive beer analysis in real time - a "beer tongue" - would be a useful quality control tool.

That's what scientists at the Universitat Autònoma de Barcelona (Barcelona, Spain) have been developing. At this point, their sensor can distinguish different varieties of beer with about 82% accuracy. Their device is based on sensing by a 21-element array of potentiometric ion-selective electrodes whose signals feed a pattern recognition algorithm.[2-3]

The ion-selective electrodes included some with response to cations, such as ammonium and sodium; and others with response to anions, such as nitrate and chloride. There were other electrodes with a generic response to other chemicals.[3] Says Manel del Valle, the principal author of the study,
"The concept of the electronic tongue consists in using a generic array of sensors, in other words with generic response to the various chemical compounds involved, which generate a varied spectrum of information with advanced tools for processing, pattern recognition and even artificial neural networks."[3]
Moritz beer and the Universitat Autònoma de Barcelona beer tongue

Ion-selective electrodes of the beer tongue, alongside a can of beer.

Moritz is a Barcelona beer brand.

(Universitat Autònoma de Barcelona image by Manel del Valle.)


The data from this sensor array give a response in a multidimensional "beer space."[2-3] The most discriminating variables were found using the Mahalanobis distance criterion.[2-3] In the end, the sensor system software was able to distinguish, with a success rate of 81.9%, some main categories of beer; namely, Schwarzbier, lager, double malt, Pilsner, Alsatian and low-alcohol.[3]

The beer tongue wasn't fooled when presented with beers outside its selected categories, or such indelectable concoctions as beer/soft drink mixtures.[3] The hope is that more advanced "tongues" of this type will replace food tasting panels as used in the food industry and will result in better food product control.[3]

References:

  1. Gilmare A. da Silva, Danilo A. Maretto, Helena Maria A. Bolini, Reinaldo F. Teófilo, Fabio Augusto and Ronei J. Poppi, "Correlation of quantitative sensorial descriptors and chromatographic signals of beer using multivariate calibration strategies," Food Chemistry, vol. 134, no. 3 (October 1, 2012) pp. 1673-1681.
  2. Xavier Cetó, Manuel Gutiérrez-Capitá, Daniel Calvo and Manel del Valle, "Beer classification by means of a potentiometric electronic tongue," Food Chemistry, vol. 141, no. 3 (December 1, 2013), pp. 2533-2540.
  3. An electronic tongue can identify brands of beer, Spanish Foundation for Science and Technology Press Release, January 30, 2014.
  4. Patrycja Ciosek and Wojciech Wróblewski, "Potentiometric Electronic Tongues for Foodstuff and Biosample Recognition—An Overview," Sensors, vol. 11, (April 28, 2011), pp. 4688-4701. A PDF file is available here.

Permanent Link to this article

Linked Keywords: Beer; beer consumption per capita; United States; blog; liter; legal drinking age; college; microbrewery; microbrew; distributor; gratis; brand awareness; brand recognition; Latin; maxim; De gustibus non disputandum est; Heineken; glass bottle; cereal; agriculture; farm; Neolithic period; brewing; steeping; food grain; water; fermentation; fermenting; yeast; chemical compound; Ethanol; b-Phenylethyl acetate; Ethyl acetate; b-Phenylethyl acetate isomer; Isopropyl acetate; Capric acid; Ethyl propionate; Ethyl caprate; 1-Pentanol; Ethyl 4-decenoate; 2-Methyl-1-butanol; p-Vinylguaiacol; Ethyl butyrate; Monoterpene; Isopentyl acetate; Ethyl hydrocinnamate; Ethyl caproate; b-Damascenone; Isooctanol; c-Nonalactone; 1-Octanol; b-Phenylethyl butyrate; Linalool; Butylated hydroxytoluene; Caprylic acid; Ethyl laurate; C8 acid; Nerolidol; C8 ester; Ethyl cinnamate; Ethyl caprylate; Caryophyllenyl alcohol; b-Phenylethyl alcohol; Oxygenated sesquiterpene; Benzoic acid; s-Cadinene; Ethyl benzoate; b-Cadinene; 1-Undecanol; Caryophyllene oxide; cis-geraniol; Dibutyl phthalate; Aromatic acid; flavor; flavoring; fruit; carbon; hydrogen; oxygen; Jynto; Ben Mills; Wikimedia Commons; analytical chemistry; laboratory; Miller Lite; quality control; Autonomous University of Barcelona; Universitat Autònoma de Barcelona (Barcelona, Spain); sensor; accuracy and precision; potentiometric titration; ion-selective electrode; pattern recognition algorithm; cation; ammonium; sodium; anion; nitrate; chloride; Manel del Valle; Moritz; Barcelona; multidimensional; variable; Mahalanobis distance; software; Schwarzbier; lager; malt; Pilsner; Alsatian; low-alcohol; soft drink.

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