Peter Reinhart posted this in his blog on 07/18/2006
Please check this
http://peterreinhart.typepad.com/pet...ugh_start.html

"wildeny" > wrote in message ups.com...

> Peter Reinhart posted this in his blog on 07/18/2006
> Please check this
> http://peterreinhart.typepad.com/pet...ugh_start.html

Yeasts are facultative aerobes, meaning that they can switch, under
certain conditions, from anaerobic metabolism to aerobic. However,
it is quite likely that dough and starter fermentations are anaerobic,
and that stirring effectively speeds fermentation by repositioning the yeast
cells with respect to their nutrients, which are depleted in their nearness
by their metabolic activities.

Drying thin layers of batter, on the other hand, might possibly involve
aerobiosis, particularly inasmuch as the diffusion path is short, practically
allowing oxygen to reach the yeast cells. Under conditions of nutrient
depletion and oxygen abundance, yeasts may (when complementary
mating strains are available) merge and sporulate. Conceivably that
could be a mechanism in SD culture drying -- but unlikely because bread
yeasts tend primarily to be polyploid, and thus incapable of the orderly
reduction division required for sporulation.

Here is some discussion:
http://www.microbiologyprocedure.com...n-in-fungi.htm

I have several (more than 6) times seen the false coming-to-life of reactivating
dry cultures mentioned by the subject author. Somewhere at r.f.s. I have
reported on that. It is my experience that there is no possibility of recovery
from it, other than back to square one. Possibly, as the author suggests, a
specific microorganism, e.g. * leuconostoc*, can be implicated.

I get depressed by statements like "yeasts need air to breathe", and "yeasts
love oxygen" as such statements imply microbiolical ignorance.

--
Dicky

"Dick Adams" > wrote in message
news:vmqvg.46$Xf.10@trndny05...

....
Yeasts are facultative aerobes, meaning that they can switch, under
certain conditions, from anaerobic metabolism to aerobic. However,
it is quite likely that dough and starter fermentations are
anaerobic,
[Agreed, except that I'm not convinced that the dough portion of the
process is anaerobic--maybe, but I'm not certain.]

and that stirring effectively speeds fermentation by repositioning
the yeast
cells with respect to their nutrients, which are depleted in their
nearness
by their metabolic activities.
[Yep. While I've not used the "aeration" method myself, yet. I'm
certain that Reinhardt is telling it as he sees it. His
"leuconostoc" approach seems to have some merit...as I seem to
recall being bit by that same thing. With a bit of success I may
get a chance to test that theory in the next few weeks...]

....
I have several (more than 6) times seen the false coming-to-life of
reactivating
dry cultures mentioned by the subject author. Somewhere at r.f.s. I
have
reported on that. It is my experience that there is no possibility
of recovery
from it, other than back to square one. Possibly, as the author
suggests, a
specific microorganism, e.g. * leuconostoc*, can be implicated.
[Yep. Same here. What I don't know for certain is would they have
"recovered" if I had waited long enough. Mostly I get mad and ditch
the lot when it doesn't work right.]

I get depressed by statements like "yeasts need air to breathe", and
"yeasts
love oxygen" as such statements imply microbiolical ignorance.
[10-4 that. I was thinking it...but have learned that many reading
here would rather bask in ignorance then have the foundations of
their "beliefs" shaken by facts...<big sigh>.

Good post, Dicky.

[L8r all,
Dusty - posting from Everett, Wa. at the moment...]

Dusty Bleher wrote:
....
> I get depressed by statements like "yeasts need air to breathe", and
> "yeasts
> love oxygen" as such statements imply microbiolical ignorance.
> [10-4 that. I was thinking it...but have learned that many reading
> here would rather bask in ignorance then have the foundations of
> their "beliefs" shaken by facts...<big sigh>.
>
> Good post, Dicky.
>
> [L8r all,
> Dusty - posting from Everett, Wa. at the moment...]

Hi Dusty,

do they? Who are they that you're afraid of upsetting? It's easy to
debate with an imaginary opponent. So what, if someone gets a bit
'upset' that you've challenged their belief. Bring it on is what I say.
I used to be a monk but I'll happily debate what people have to say
about the subject without any attachment. Sometimes chuckling to myself
though, even scientists can come out with superstitious, unfounded,
ignorant crap. The times I've heard some well know phd talk about
something as though it were inherent. What gets my goat though is when
some just says "Pile of Crap" then signs off. What use is that? And
what's more frustrating I've seen some of the more intelligent and well
read posters doing it.

If you're going to refute someone's statement, and again, bring it on,
then do it with reason. Then what does it matter if someone gets their
knickers in a twist? They'll probably be glad if it later. And if they
aren't, tough. You can't please everyone or control their thoughts.
We've had our differences but honestly Dusty, I don't have any bad
feelings towards you, Dickey or anyone else. You've told it like you
think it is many times. Though I haven't always agreed with what you've
said it's been worth saying and often made me re-evaluate my opinions
on the subject. I think that's great. If it weren't for you, Dickey and
some of the others I'd still be using the sponge technique and
listening to old grannies going on about what their granny did. lol

TG