July 23, 2009 - 10:20am
trapped gas in starter build container
The container that I use to store my intermediate starter build has a tight sealing lid. After it's been fermenting for awhile the lid bulges and "pop"s when I release it, indicating a gas buildup trapped in the container. I wonder if that has any effect, pro or con, on the starter development.
:-Paul
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The answer to your question is, "Yes." The explanation will have to come from Debbie Wink or one of the other microbiologist on this forum. (Perhaps Dan or SteveB know the answer too.)
See the article here.
--Pamela
Or maybe I'm a bit thick. I'm not techno-savy enough to get that article, but it does look like there's some effect anyway. I imagine that the level of concentration that occurs with a home container jar lid seal might not be enough to matter, experimentally, but I wonder; when I hear that "pop" - is it a good thing or a bad thing? This is an intriguing line:
Ya gotta wonder what they mean by "promising" - would that be from a commercial, mass-production viewpoint, or a taste standpoint or what. Are the red, rock-hard things called tomatoes in the grocery store the result of "promising new" techniques? They ship well, you just don't want to eat them.
:-Paul
Sorry Pamela, I don't think I can really be of much help. I don't have access to the entire article, but I can tell you that L. amylovorus is not one of the lactobacilli found in the type of starters that we home bakers keep, so the information therein doesn't really help us anyway. But it helps the scientists who are trying to generate specific compounds in industrial sourdoughs. Dare I call them... "designer"?
I can guess that CO2 pressure probably has some effect on the organisms, but couldn't predict with any certainty how it will impact any particular species that may be in Paul's starter. I think repeating what David said is about the best I can do, which is that if the CO2 pressure above the starter is high, then more CO2 will remain dissolved in the starter (increasing carbonic acid). But, that may or may not be the only effect.
-dw
Love your tomato comment. Hopefully Debbie Wink will shed some light on your question.
--Pamela
the effect on the starter itself, is secondary. However, if you think it through you're building up pressure in the container. Consequently, the starter mass won't expand as much as it would at normal pressure--that's just the physics of gases, and has nothing to do with the starter beyond it being the source of the gas. So doubling in the sealed container would be greater in a loose-lidded container.
Secondly, sourdough book authors often stress maintaining starters in loose-lidded containers, and the starter vendor I purchased one of my starters from instructed keeping the lid loose for safety reasons. The built up pressure may be sufficient to break a glass container.
But, my question Paul, is why do you feel it necessary to seal your build container tightly? A loose lid, and the internal gas pressure will emulate a clean room--the internal pressure will resist any air carried contaminent from getting in.
I build my formula-ready starters in a loose lidded container, and I keep the lids on my refrigerated starter containers loose for 24 to 36 hours after I refresh them. Only after the cold starters have gone dormant do I seal the lids tightly.
David G
I thought you had written about your build contianer. Mea culpa. Oops. Now I'm confused, I read it again, and now I'm not sure of which container your speaking: building or storing.
David G
I think Paul is just interested if the build-up of CO2 in the starter container has any effect. And apparently it does have some effect. It is an interesting question (at least to me and I hope to Paul). (Of course, we all know how to avoid the build up ....)
--Pamela
I do find it interesting. I'm wondering if there's a pro or con reason from the starter's perspective. Certainly from my perspective I wouldn't want anything breaking.
The container is used during an intermediate build - having fed the starter in preparation for using it in a dough. Think Detmolder. I've taken to floating the container in 70F water in the bathroom basin as the room temp has been in the 80s. I don't want to use the 'fridge as it's too cold. The sealed lid insures that water won't get in the container. Certainly it doesn't NEED to be sealed, but since it came up, I'm wondering about the possible effect on the starter's performance.
:-Paul
Paul,
In all my reading about starter behavior I haven't seen anything relating to the effect of gas pressure build up on yeast performance, but my reasoned suspicion is it has some effect, but how much would require a controlled experiment beyond the capability of most of us. My reasoning is, in a sealed container CO2 in greater concentration will remain surrounding yeast cells than in an unsealed container. The CO2 is dissolved in the dough's water content, it is not yet in gaseous state. I suspect the increased CO2 would cut off individual cells access to sugar molecules faster, but it may be only a negligible difference.
Another way to cool your container, without putting it in the refrigerator is wrapping it in a single layer of a dampened towel, or cotton cloth. The water evaporation from the cloth will cool the container unless the air's humidity is 95 to 100 percent. Homebrewers sometimes use this trick to cool fermenting wort when the room temperature is high. You have to keep the cloth damp however.
I think the final answer is, if what your doing is working for you, stick with it.
David G
Thanks for the cooler trick, David. I grew up in Bakersfield, CA, where summers were very hot. We had no A/C, just evaporative coolers. They worked great. I'll try that, it's nice and homey feeling.
:-Paul
I spent a summer riding from San Diego to the Bay Area every Friday night, and returning on Sunday in an unairconditioned Volkswagon beatle, crammed in with four other guys, up the old Grapevine through Bakersfield and Fresno. It gave a new meaning to the hot and sweaty.
David G
Bakersfleld, CA! Well that explains everything.
--Pamela
hope Paul thinks so too.
David G.
It's not called Baker's field for nothing.
--Pamela
It's in my Jeans. The ovens come preheated in the summer.
:-Paul
I think you've definitely got everything figured out now.
--Pamela
I'm from SF and think I wouldn't like that homey feeling. --Pamela
If the volume you are building is small, you could do what I do with my mother starter and use wide-mouth canning jars with two-piece lids. This is exactly what they are designed to do---vent pressure out, while keeping water (or air) from getting in. The lids are cheap, and they work very well.
For larger volumes, if you use a wide plastic container with head space, you should be able to float it in the water bath like a boat, without worrying about water getting in.
I'm still not clear whether there is a definitive answer here regarding any negative effect of CO2 buildup in a sealed jar. I've often read that your dough should be periodically degassed as the CO2 inhibits the growth of yeast cells. That being the case, is it not a good idea to keep a levain in a sealed canning jar? In particular, I started keeping my stiff levain in a canning jar and it built up enough pressure overnight to hiss when I popped the cover. (The only reason I started doing this is because evaporation would cause it to really dry out in the fridge in a container with a loose-fitting lid).