hist-brewing: aerobic fermentation and Fermax

BrewInfo brewinfo at xnet.com
Mon Jul 12 12:16:47 PDT 1999

Mel writes:
>What is Fermax ? Chemically ?

This is the Historical Brewing Digest, so I won't go into a lot of
detail.  If you really need to know exactly, you can contact Siebel
and Sons in Chicago (mfg) or Crosby & Baker in Westport, MA (distributor).
Basically it is (from appearance and smell): diammonium phosphate,
yeast extract and probably a few vitamins other trace minerals.


Dan writes:
>If all you want is speed, raise the temperature and keep
>bubbling oxygen through it throughout the entire fermentation
>(the aerobic fermentation uses up sugars much faster than
>the anaerobic stage, so it'll ferment out sooner).  Sure, you'll
>probably end up with undrinkable cardboardy mead with plenty of
>rotting cabbage esters and fusel alcohols, but just think of the
>time you'll save.


Look at it as two stages:
>____Stage 1: Propogation (aerobic fermentation)___
>Input: yeast                Yields: more yeast (a lot)
>       sugar (a lot)                alcohol (a little)
>       oxygen (a lot)               CO2
>Then when there is a sufficient yeast colony (I guess the
>cells have a board meeting to determine this, then send out
>a memo), it moves on to the second stage:
>____Stage 2: Fermentation (anaerobic fermentation)_____
>Input: yeast                Yields: more yeast (only a little)
>       sugar (not as much)          alcohol (a lot)
>       oxygen (only a little)       CO2

Again, this is the *Historical* Brewing Digest, so we are getting
off the subject, but I would like to set the story straight.

Saccharomyces yeast exhibit what is known as the Crabtree Effect
(also called Reverse Catabolism, I believe).  The Crabtree Effect
is where the yeast forgo respiration (aerobic fermentation) and
go straight to anaerobic fermentation, even though there is oxygen
present.  Glucose, in concentrations of 0.4% w/w (if memory serves
correctly) or higher induces the Crabtree Effect in Saccharomyces, although
other sugars (maltose, for example) also induce the Crabtree Effect
to a lesser extent.  Yeast still really desire oxygen (for sterol
synthesis, for example) and will absorb virtually all the O2 you give
them, but only a very small amount (less than 10%) will actually
be used for aerobic fermentation in a real-world situation.  See
Malting and Brewing Science by Hough, et al for more details.

Sorry about clogging up the Historical Brewing Digest with all this


Al Korzonas, Lockport, IL
korz at brewinfo.org

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