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Biochemsitry notes

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  • Tony & Elle Ackland
    Some new things I ve just read / forgotten stuff revised, that you might find useful .... 1) yeast produces 33 times more alcohol while reproducing than when
    Message 1 of 2 , Feb 3, 2001
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      Some new things I've just read / forgotten stuff revised, that you might
      find useful ....

      1) yeast produces 33 times more alcohol while reproducing than when resting
      (so most of the gains are in the first couple of days, then you're just
      relying on the large numbers of yeast finally present to slowly work their
      way through the remaining sugars)

      2) you end up with about 2g per litre of yeast (eg 40g in a 20L wash) This
      is why you don't get the full 51.1% conversion of sugar to ethanol, and
      gives some idea of the amount of nutrients - particularly nitrogen - that
      you need to supply.

      3) fusel oil concentration in the wash can be up to around 0.24 g per Litre
      from 20% sugar (eg about 3.2 mL from a 20L wash)

      4) fusels increase depending on ...
      * yeast strain (eg Saccharomysce cerevisia makes more than
      S.carlsbergensis)
      * temperature (higher temp = more fusels)
      * increased aeration and agitation (news to me ! so don't over-stirr
      it !)
      * wort composition (nitrogen sources and readily metabolised sugars)

      5) the most common limiting factor for yeast growth is a lack of nitrogen.
      Nitrogen is approx 9% of the cell mass. Most common form to add it is as
      the ammonium ion, as the sulphate and phosphate salts (phosphorus is
      approx 1-2% of the cell mass, and sulfur 0.3-0.5% so these are needed too -
      this is a nice way of getting all three in there)

      6) the second most common limiting factor is a lack of oxygen, but it only
      needs it until high cell numbers are present (eg during the first day) (so
      make sure that you've aerated the wash well just prior to adding the yeast,
      but don't do this too much later in the game) "Splash filling" is enough
      to do the job.

      7) bacteria can double in number every 20-30 minutes, but yeast takes 3
      hours (so guess which one will win the race if an infection gets started
      and you don't deal to it)


      Tony
    • stampers@bigfoot.com
      ... might ... Wow! Too right it was useful stuff. You amaze me with the amount you know on this subject, but it s nice to know there s still things to learn,
      Message 2 of 2 , Feb 4, 2001
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        --- In Distillers@y..., Tony & Elle Ackland <Tony.Ackland@c...> wrote:
        > Some new things I've just read / forgotten stuff revised, that you
        might
        > find useful ....

        Wow! Too right it was useful stuff. You amaze me with the amount you
        know on this subject, but it's nice to know there's still things to
        learn, or re-learn.

        More power to your elbow!

        Kev.
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