Sourdough low innoculation recipe tradeoffs
Hi all - love this forum and just joined after reading it for many months. I've read through Debra Wing's posts that I could find and a majority of others and it's been super informative to learn the microbiology of sourdough fermentation.
I noticed in the past year or two there have been a few recipes posted by what I consider respectable folks where instead of using an active/strong starter, you just stick yours in the fridge once it's rising/peaked and then use it within the next week right out of the fridge at a low innoculation %. These recipes are marketed as "same great loaf with less fuss!" and basically the idea is you don't have to maintain a daily starter feeding and the only downside of this method is a longer fermentation time.
https://www.kingarthurbaking.com/blog/2022/05/17/how-to-bake-sourdough-bread-without-feeding-starter-first this one is 4% innoculation
https://newsletter.wordloaf.org/p/thursday-recipe-the-loaf?s=r 6% innoculation
My understanding is this:
Once you inoculate your flour, fermentation is a race between yeast and bacteria. So having a "strong" starter gives the yeast get enough of a head start such that the bacteria don't get ahead and make the dough too acidic for the yeast to achieve maximum peak.
In other words (and I'm totally making up numbers assuming a 1:100 ratio of yeast to LAB cells)
If you do a 20% inoculation, for a weak starter you might come in with 5 yeast microbes and 1k LABs. Strong starter you could be, let's say, at 20 yeast vs. 10k LABs. So with the weak one, the ratio of LABs:yeast is way higher and thus the LABs reproduce/generate acid at a faster rate and don't give the yeast a chance to hit max peak, assuming constant temp, let's say 80F.
So if you're doing a 5% inoculation, isn't it the same concept but it just takes longer for the same things to play out? Meaning, ok maybe you're starting out with 1 yeast and 200 LABs (weak) vs. 4 yeast + 200 LABs (strong). But assuming same flour, same temp, it will take longer but the LABs still have the same *relative* head start as the 20%?
Another way of asking my question: when it comes to maximizing oven spring, is there really no trade-off besides the fermentation time when we're talking about something like a 5% unfed inoculation out of the fridge vs a 20% strong daily fed starter? It just seems too good to be true, at least for a home baker that's not concerned with fermentation timing as much.
Thanks in advance for input.
"...fermentation is a race between yeast and bacteria".
Isn't a sourdough starter, and similarly the resulting dough, a symbiotic culture of bacteria and yeast? Does something that's symbiotic have a race going on? I would have thought it would be the exact opposite.
Doesn't a stable starter have 100:1 bacteria:yeast?
I may be wrong however whatever amount of starter goes into the dough the dough is ready when it's ready. If more goes in it's ready in less time. If less goes in it takes longer. Oven spring is maximised when it's fermented to the correct amount.
The reason why you use less starter the more mature it is, i.e. the longer the time has passed since it was last fed, is because of acid build up, off flavours and degradation. If you use a large percentage of over fermented starter it'll have a detrimental affect on flavour, gluten and power. So you use less. The fresher it is it's more flavourful and the gluten hasn't broken down so more can be used in the final dough. I don't think you have to be concerned about anything else other then that. The bacteria and yeasts sort themselves out as long as you follow that rule of thumb.
Of course you can upset the fine balance of a starter through poor maintenance and neglect but that would just be an unhealthy starter. As long as your starter is properly maintained it'll do the rest. You're just their to feed it. For millennia they made sourdough bread without knowing what yeast and bacteria were.
Ah! This is a helpful framing, thank you. To parrot back what I think you said:
The "strength"/freshness/ripeness of a starter is not necessarily about yeast vs. bacteria subverting each other depending on which one is "favored", it's more about acid buildup and the effect on other things in the dough like gluten. And focusing on the acid makes sense here because we know having too much or too little yeast isn't (generally) much of an issue in terms of quality, more of timing. Maybe flavor, to some extent.
So the term "strong starter" can almost be flipped on its head - a strong starter is one that has weak LABs that allow the yeast to shine, in a sense.
But if you do a low inoculation %, the strength of the acid matters a lot less because it's a small quantity being added to the dough. As far as what happens after inoculation, the yeast and bacteria will both do their thing as usual, it will just take longer vs. adding a higher %.
Hopefully I got that generally right, let me know if I didn't. Thank you for answering my question!
That is 'generally' a good way to think about it. Another way is a starter has a natural balance. Roughly 100:1 bacteria vs. yeast (although the yeasts are many times bigger than the bacteria). Being symbiotic it cannot favour both at the same time. When fed it'll mature and once it is ripe it is the best time to use. Once it gets over ripe the acids begin to build up. So a freshly fed mature starter one can use in larger quantities. A starter that has been fed sometime ago and has been sitting in the fridge for a while should either be fed before using or used in small quantities due to off flavours and high acidity which will be detrimental to the final dough.
I would say a strong starter is one that is well balanced. Recently fed and not overly ripe. Just peaked. If you think about it a dough is a big feed and a piece of dough is often used as a starter for the next batch.
What happens if a starter hasn't been fed in a long time? You dump most of it out and give it a healthy feed of fresh water and flour. Exactly what is happening inside a dough. So if you use starter straight into the final dough without refreshing, and it hasn't been fed in a long time, then best to use smaller amounts.
You can get strong leavening starters, like lievito madre, which are kept in such a way that keeps the acidity low. It is a sourdough starter and whether this means the bacteria are kept in check and the number of yeasts high i'm not sure. I'm inclined to think they still have a symbiotic balance but that is another ball game.
Debra Wink and Michael Wilson will be able to go into this whole topic in greater details.
Here is a nice recipe using a very small quantity of starter.