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Re: [S] [Distillers] Re: Wash temp.

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  • Bob Bourne
    33C and Harry s mercaptans ? The optimum temperature for fermentation if one is thinking of speed rather than flavour is about 33oC. From John Stone s
    Message 1 of 3 , Aug 4, 2004
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      33C and Harry's "mercaptans"?

      "The optimum temperature for fermentation if one is thinking of speed rather
      than flavour is about 33oC."
      From John Stone's Making Gin & Vodka.

      The idea seems to be (using baker's yeast here) the nasties are left behind
      on distillation. I'm talking about making vodka only here. Are the
      mercaptans left behind on distillation?

      Comments appreciated.

      Cheers,
      Bob.

      snip -
      > Pretty much. You can chill it to drop out the yeast. But if you
      > let it get too warm, like 30 deg C, then any residual yeast (always
      > some) will be under severe stress and produce nasties like
      > mercaptans.
      >
      > Slainte!
      > regards Harry
      >
      >
      >
      >
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    • Harry
      ... speed rather ... left behind ... Hi Bob, There s not a great deal of info around re mercaptans and distilling. However it s well documented in the wine
      Message 2 of 3 , Aug 4, 2004
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        --- In Distillers@yahoogroups.com, "Bob Bourne" <bourne@v...> wrote:
        > 33C and Harry's "mercaptans"?
        >
        > "The optimum temperature for fermentation if one is thinking of
        speed rather
        > than flavour is about 33oC."
        > From John Stone's Making Gin & Vodka.
        >
        > The idea seems to be (using baker's yeast here) the nasties are
        left behind
        > on distillation. I'm talking about making vodka only here. Are the
        > mercaptans left behind on distillation?
        >
        > Comments appreciated.
        >
        > Cheers,
        > Bob.



        Hi Bob,
        There's not a great deal of info around re mercaptans and
        distilling. However it's well documented in the wine industry, and
        wash is essentially a wine. I got hold of a couple of things worth
        keeping...

        http://winemakermag.com/mrwizard/169.html

        <ext>
        The second possible cause is hydrogen disulfide or mercaptans. There
        are numerous potential pathways for these stinky compounds to get
        into your wine. Sulfur spraying in the vineyard too close to the
        harvest date is one possibility.

        Yeast spit out elemental sulfur in the form of hydrogen sulfide.
        Other causes might include insufficient nitrogen levels during
        fermentation, high fermentation temperatures, low fermentation
        temperatures, a too-rapid fermentation or anything that will stress
        your yeast out.

        Most often, hydrogen sulfide smells like rotten eggs and mercaptan
        smells kind of oniony, but I've seen them develop into burnt rubber
        aromas in finished wines.

        Sometimes hydrogen sulfide and especially mercaptans can't be
        removed at all and even professional folks have to live with the
        stinky results of naughty yeast. Never fun, but a reality of the
        business.
        </ext>

        And from the Homebrew Digest, an extremely good article on yeasts,
        like EC-1118, this extract...
        http://hbd.org/hbd/archive/3308.html

        <ext>
        Except for a few mutated yeast, H2S is a natural metabolic pathway
        in the production of two of the sulfur containing amino acids. The
        big problem is to minimize the excess production of H2S. An
        adequate supply of nitrogen (DAP and autolyzed yeast) throughout the
        first half of the fermentation goes a long ways to achieve this. An
        unhealthy yeast cell will die prematurely and cause the production
        of mercaptans (sulfury type compounds)
        at the end of the fermentation.
        </ext>




        So if you want your wash smelling like rotten eggs, or onions, then
        go ahead and ferment hard and hot, or stress your yeast with under-
        nourishment.

        As to whether it carries over in distillation, well I don't rightly
        know. I have this info from the online encyclopedia...
        http://52.1911encyclopedia.org/M/ME/MERCAPTANS.htm

        <ext>
        They are colorless liquids, which are insoluble in water and possess
        a characteristic offensive smell. On oxidation by nitric acid they
        yield sulphonic acids. They combine with aldehydes and ketones, with
        elimination of water and formation of mer-captals and mercaptols.

        Ethyl mercaptan, CjHs.SH, is a colorless liquid which boils at 36.2
        C. It is used commercially in the preparation of sulphonal.

        The mercury salt, Hg(SC2H6)2, crystallizes from alcohol in plates.
        When heated with alcohol to 190 C. it decomposes into mercury and
        ethyldisulphide.
        </ext>


        From that info I assume that while it has a low boiling point and
        MAY be driven off early in distilling, it also is capable of
        combining with ahdehydes and ketones, both of which are present in
        malt whisky. That makes me think that it probably will carry over.
        I've never noticed any rotten egg or onion smells from any of my
        whiskies.

        HTH
        Slainte!
        regards Harry
      • Harry
        Further evidence that it does carry over... FEDERAL REGULATIONS 24.247 Materials authorized for the treatment of distilling material. Copper sulfate: To
        Message 3 of 3 , Aug 4, 2004
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          Further evidence that it does carry over...


          FEDERAL REGULATIONS
          24.247 Materials authorized for the treatment of distilling
          material.

          Copper sulfate: To eliminate hydrogen sulfide and mercaptans.

          The finished brandy or wine spirits produced from distilling
          material to which copper sulfate has been added shall not contain
          more than 2 parts per million (2 mg/L) residual copper. GRAS per FDA
          advisory opinion of 7/23/69.

          Source:
          http://www.wineinstitute.org/fedlaw/regs/27cfr_part24/24_247.htm


          Slainte!
          regards Harry
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