1
$\begingroup$

Given a sample of an alcoholic beverage (be it beer, wine, etc..), what are possible methods to find out the ABV (alcohol by volume) of it with moderate accuracy?

As fas as I know, some methods exist already but are not really suitable in my condition:

  • Distillation. Impractical because of the apparatus needed
  • Boiling temperature based. Not accurate if exact condition of sugar is not known
  • Estimation by measure of specific gravity before and after fermentation. I've found it to be inaccurate with the data I have access to

I was thinking about a process similar to the tritation method used to find water hardness, but I'm not sure what kind of reactions would be involved for this kind of test, nor the nature of the titrant that would be required.

$\endgroup$
3
  • 1
    $\begingroup$ What, pray tell, is "estimation"? ;) Anyway, you have missed the most commonly used methods used in the production of wine, beer, etc. You should read a bit more. $\endgroup$ – Karl Jan 23 '20 at 21:27
  • $\begingroup$ "Estimation" meaning use of a function of density before and after the fermentation (en.wikipedia.org/wiki/…). However, I've found them to be quite inaccurate. If you say I've missed a method, would you be so kind pointing me to it, so that I can research it further? $\endgroup$ – Mauro F. Jan 23 '20 at 21:36
  • 2
    $\begingroup$ OK, but "estimation" just means "a method that gives a rough first guess". Density is one, refractive index another, and optical activity tells you how much sugar you have (if you know what sugar it is). I guess you can use that to correct the values from density and refractivity measurement. $\endgroup$ – Karl Jan 23 '20 at 21:53
4
$\begingroup$

Your question: Given a sample of an alcoholic beverage (be it beer, wine, etc..), what are possible methods to find out the ABV (alcohol by volume) of it with moderate accuracy?

There are a few method used in winery industry as Karl mentioned a comment in elsewhere. I assume you want to find out better methods to find the alcohol content:

  1. The best technique is the gas chromatography method, which is the most accurate method for determining alcohol content. Gas chromatography has the added benefit of providing additional information about the wine, beer, or any other liquor product (e.g., Ref.1).
  2. Seemingly most popular technique is the determination of ethanol in alcoholic beverages by titrimetric and/or spectrophotometric dichromate methods (e.g., Ref.2-Ref.4).
  3. Another method is enzymatic assay using spectrophotometry: Ethanol, in an alkaline environment, is oxidized through an enzymatic reaction and converted in acetaldehyde in presence of $\mathrm{NAD^+}$, which in turns produces $\mathrm{NADH}$. The increase of the absorbance, measured at $\pu{366 nm}$ (end-point), is proportional to the concentration of ethanol in the sample (e.g., Ref.5).
  4. In addition, you can also use NMR technology to determine the ethanol content in alcoholic beverages (e.g., Ref.6).

References:

  1. M.-L. Wang, Y.-M. Choong, N.-W. Su, and M.-H. Lee, “A rapid method for determination of ethanol in alcoholic beverages using capillary gas chromatography,” Journal of Food and Drug Analysis 2003, 11(2), 133–140.
  2. G. J. Pilone, “Determination of ethanol in wine by titrimetric and spectrophotometric dichromate methods: collaborative study,” J. Assoc. Off. Anal. Chem. 1985, 68(2), 188-190 (https://www.ncbi.nlm.nih.gov/pubmed/3988696).
  3. Arthur Caputi, Masao Ueda, Thomas Brown, "Spectrophotometric Determination of Ethanol in Wine," Am. J. Enol. Vitic. 1968, 19(3), 160-165 (https://www.ajevonline.org/content/19/3/160).
  4. Malinee Sriariyanun, Parita Mutrakulcharoen, Surapun Tepaamorndech, Kraipat Cheenkachorn, Kittipong Rattanaporn, "A Rapid Spectrophotometric Method for Quantitative Determination of Ethanol in Fermentation Products," Oriental Journal of Chemistry 2019, 35(2), 744-750 (http://dx.doi.org/10.13005/ojc/350234).
  5. Amy A. Caudy, "Spectrophotometric Analysis of Ethanol and Glucose Concentrations in Yeast Culture Media," Cold Spring Harbor Protocol 2017, (9), 735-741 (doi: 10.1101/pdb.prot089102).
  6. Meden F. Isaac-Lam, Thomas Brown, "Determination of Alcohol Content in Alcoholic Beverages Using 45 MHz Benchtop NMR Spectrometer," International Journal of Spectroscopy 2016, Article ID 2526946, 8 pages (https://doi.org/10.1155/2016/2526946).
$\endgroup$

Not the answer you're looking for? Browse other questions tagged or ask your own question.