Determining ethanol and methanol content in homemade booze

  1. Hi, I've recently made some very budget homemade 'beer', butt i'm wondering is there an easy (doesn't have to be accurate) way to determining ethanol and methanol content. any help appreciated.
     
  2. jcsd
  3. Borek

    Staff: Mentor

    Nothing easy and obvious. Ethanol can be estimated by measuring the density, assuming no methanol present (or present in negligible quantities). Methanol is a problem in general, as far as I remember nothing below mass spectrometry is reliable.
     
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  4. :/ Ja, I was thinking specific gravity for ethanol content but the methanol is the issue as you say. Just don't want to go blind and die from methanol poisoning. Thanks though.
     
  5. AlephZero

    AlephZero 7,298
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    In fermentation, methanol is produced from pectin. If you ferment materials that have a high pectin content (e.g. fruit, rather than grain) the methanol content will be higher, but it's unlikely to be a health hazard. You can reduce this by adding "pectic enzyme" (trade names pectolase, pectinase, etc) to break down the pectin before it ferments. It is more of an issue in wine making that brewing.

    If you are distilling fermentation products, methanol is a much more serious issue - but that is probably an illegal activity, so not a topic for discussion on PF.
     
  6. Borek

    Staff: Mentor

    In many countries it is illegal, but as far as I understand in some it is not.
     
  7. AlephZero

    AlephZero 7,298
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  8. I'm not distilling don't worry
     
  9. Bystander

    Bystander 3,774
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    Freezing point depression.
     
  10. Borek

    Staff: Mentor

    Just like density measurement, it requires assumption nothing but ethanol is present. Any other solute and the result is off.
     
  11. DrDu

    DrDu 4,452
    Science Advisor

    Beer contains also lots of sugar. So you have to separate the alcohol off before you can quantify it, e.g. by distillation.
     
  12. im only using water yeast (added vitamin c)and sugar.
     
  13. DrDu

    DrDu 4,452
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    How do you know how much of the sugar is consumed by the yeast and how much is left?
     
  14. Bystander

    Bystander 3,774
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    OP wants an "easy" method: evaporate the filtered product to determine dissolved solids; do a freezing point depression to determine total concentration of dissolved materials; difference is concentration of volatiles.
     
  15. epenguin

    epenguin 2,328
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    Pretty certainly the method is going to be enzymatic. Finding an enzyme and reagents that will convert the alcohols into something easily detectable and measurable - something coloured. The problem is do they have one that works on methanol and not ethanol? - lots of enzymes will work on both. Just google 'methanol assay' and you find a lot. And they even sell kits for it apparently, see last ref. below.

    I would advise not to use a kit or method without validating it yourself with samples of known methanol and ethanol contents, - test on each alcohol separetely and mixed.

    I haven't gone beyond that but quickly turned up this:

    http://www.biovision.com/alcohol-dehydrogenase-activity-colorimetric-assay-kit-4164.html


    http://www.biovision.com/ethanol-colorimetric-fluorometric-assay-kit-2915.html

    Applied Biochemistry and Microbiology
    November 2002, Volume 38, Issue 6, pp 607-609
    Photometric Assay for Methanol in the Presence of Ethanol
    Comparison of Three Colorimetric Reagents in the
    Determination of Methanol with Alcohol Oxidase.


    1. Photometric Assay for Methanol in the Presence of Ethanol - Springer
    link.springer.com/content/.../A:1020747215826.pd... -
    di YV Rodionov - ‎2002 -
    ethanol and methanol, involving electrochemical detec- tion of changes in O2 or ... assay of methanol and ethanol in solutions containing both these alcohols.
    2. An enzymic assay for the specific determination of methanol in serum.
    www.ncbi.nlm.nih.gov/pubmed/3319289‎
     
    Last edited by a moderator: Mar 4, 2015
  16. Borek

    Staff: Mentor

    Really? Imagine you have 100 mL of water solution containing 1.00 g of mixture of sucrose, glucose and NaCl. Please calculate its freezing point depression - that will convince me your method will work.

    To make things simple, feel free to ignore creation of ionic pairs.
     
  17. Bystander

    Bystander 3,774
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    Step 1), f.p. depression; step 2), evaporate water and alcohols from a weighed sample, and weigh the residue (a mixture of who knows, or cares, what); step 3) subtract the 0.3 to 0.5 K contribution to total depression from the 2 to 2.5 (maybe 3 K) depression measured in step 1). 10% uncertainty plus another 10% for working on the kitchen counter --- close enough for home brewing.

    For the obsessive-compulsive, redissolve the weighed residue from step 2) in water to equal the original sample weight and determine the depression due to non-volatile dissolved solids (given that biologic activity doesn't modify things too much).
     
  18. Classical detection is supposed to be oxidation to aldehydes with air and hot copper wire - methanol should go to formaldehyde and ethanol to acetaldehyde, and the smell of formaldehyde should be different. But is this reliable/quantitative?
     
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