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Re: DIY CO2 turning pink

>> Perhaps a chemist out there can give you a reason for "pinkness."
>I suspect that a biologist might have more to say about it.  

I'm a biologist, but not really the right kind.  :-)  

I also have had my mixture turn pink, but only once when I let it go after
the yeast had ceased producing CO2.  I'm sure that those who have mentioned
this earlier were correct, the pinkness is due to bacterial growth.  In
normal circumstances the yeast, due to their large starting culture,
outcompete any bacteria that may be present.  However, once the yeast loose
their competitive advantage, either due to the increase of EtOH that
eventually kills them or some other reason, the bacteria take over, and may
turn the mixture pink depending on the type of bacteria that becomes
dominant.  (BTW, we have some species of bacteria here in Houston that
grows in moist places around the house and turns everything puke orange; I
wouldn't be surprised if the pink color is from the same species.)

Reasons besides increasing EtOH concentration that may cause a bacterial
takeover would include a very large contamination by bacteria (rinsing the
bottle and any utensils used to fill it before hand should eliminate this)
and heating the water too much during preparation.  Very hot water will
kill the yeast, leaving the sugar solution free to any bacteria that happen
to survive the heat or be introduced later.  I suppose that more exotic
reasons, such as the use of detergents or other chemicals that kill the
yeast but not (all) the bacteria, are possible as well.

Chetlen Crossnoe
Baylor College of Medicine
Structural and Computational Biology and Molecular Biophysics
cc691077 at bcm_tmc.edu
"All the things that God would have us do are hard for us to do."
                                                     -- Melville