Airtight starter container?

Like everything else, there's going to be disagreement depending on who you ask but...

no, you shouldn't  store starter in an airtight container.

The starter needs air to do its thing to populate. I keep mine in a glass jar with a lid.  Between bakings, I store mine in the refrigerator with the lid on.

No, you should not use an air tight container because the starter generates a gas (carbon dioxide) and the pressure could build up in the container and result in a minor disaster in your refrigerator.

I do disagree that the starter needs air to propagate.  It can propagate and metabolize the flour either with oxygen or without.  In dough the  lactobacteria rapidly use any dissolved oxygen and then metabolize anaerobically.

Debra Wink wrote,

"Some pathways generate more energy than others. Through respiration, glucose and oxygen are turned into carbon dioxide and water via the Krebs cycle, also called the tricarboxylic acid or TCA cycle. You may have seen it before if you've studied biology, because it's the same pathway we humans use. It is aerobic, meaning that oxygen (O2) is involved, and it generates far more energy than any fermentation pathway. Whenever oxygen is available, respiration is favored by facultative anaerobes like yeasts, because they will always take the path that generates the most energy under the prevailing conditions. For the most part though, bread dough is anaerobic (without oxygen), and fermentation is an alternative pathway that doesn't require oxygen. When yeasts ferment sugars, they produce alcohol (ethanol) in addition to carbon dioxide. Fermentation produces much less energy than respiration, but it allows microorganisms to carry on when no oxygen is available, or they lack the ability to respire as is the case for lactobacilli."

See:  http://www.thefreshloaf.com/node/10375/lactic-acid-fermentation-sourdough

Ford

For whatever reason, here's a third vote for "NO"  -  don't build or store your starter in an air tight container.  As the CO2 develops, so does the pressure inside the container.  That means, in an air tight container, you're building pressure against the starter's desire to increase in mass.  Kinda like trying to inflate a baloon inside a jar.  At some point the pressures will equalize and stiffle the growth.

The trick is - what do you mean by "airtight"?

I keep my starter in a Cambro container.  These are commonly described as "airtight" - but they are not.  The lids allow just enough leakage that my starter can double without any issue.  There have been warm days when I have overfed the thing that the top will blow off, but about 362 days of the year everything is ok as long as I don't let the starter get too large for its home.

My starter lives free range in my kitchen and is fed daily. Which also means it never gets more than about 24 hours buildup of anything.

The container is handy and my starter has lived in it or one similar (gotta wash that thing sometimes) for over ten years.

Now if you talk about really airtight - like a canning jar with a propely installed ring, or one of those vacuum seal containers - no, I would not do that for all the reasons above.

Hope this helps.

I keep my starter in the refrigerator, and, at or below refrigerator temperature (~40°F) it  ultimately goes dormant, but it takes about three days to reach dormancy after its weekly feeding. I keep my starter in a canning jar. After feeding I leave it on the counter for an hour to ensure it is still active--after feeding I mark its height with a rubberband stretched around the jar. As soon as I see expansion, evidence of activity, I put it in the refrigerator with the its  lid only partially tightened; i.e. not airtight. Over the next two or three days I see about a doubling of expansion, then a collapse. At that point I screw the lid down tightly. I believe, at that point, the jar is airtight, and the yeast is dormant, or nearly so. (Yeast growth vs. temperature curves I've found online support my belief.) When I feed them, or use them, next there is no apparent pressure build up.

I don't think it matters much that I tighten the lid, but it ensures the environment inside the jar is as stable as I can make it in a home kitchen. If nothing else, it gives me peace-of-mind my starter is relatively safe.

David G

I think the answer depends on what you're doing with the starter.  If it's sitting on the counter overnight, then don't seal it tightly for all the reasons mentioned above.  However, when you put it in the fridge it's growth is slowed so much that there's really little risk to putting a lid on it, even if it continues to grow for a day or two.  I put mine in the fridge in a glass "rubbermaid" bowl with a plastic snap-on top, and it has never, ever given me a moment's trouble.

I feed my starter about once a week. In the interim, I keep the starter in the fridge, in a rubber sealed canning jar. The type with the wire ring.

After feeding it, I keep it out for about an hour and then relocate it to the fridge where it will ultimatley find dormancy. The starter is never more than half the volume of the container. During the first 3 to 4 days after feeding, I will open the jar daily to exchange the CO2 for fresh air. This seems to work best. Although, Proth5 has the best set up, a cambro.

Happy baking.