and the started revived!
Hi all,
I'm starting in the new world of sourdough baking and I've noticed something odd.
I've seen in many threads that the reason why the started peaks and starts to fall is because the yeast/bacteria have run out of food and started dying and collapsing. That's why at this point or a bit earlier is the best time to use to make a bread.
Well, I've noticed that after this point when the yeast/bacteria is supposed to have run out of food, if you stir again the starter to the point where it's texture is close to the original one (no adding more flour nor water), it behaves the same way and revives! It rises again x2 or x3 times its volume as if nothing had happened! This makes me think that there must be still "food" in the starter...
Has anyone had seen that before? Any sensible explanation for it?
I remember to have read somewhere that if you have an over-proofed loaf that has collapsed you could shape it again and it'll be just like newly shaped. So perhaps this is the same?
Cheers
I recently, in the last week or so, saw that same thing happen and intended to post that asking the same question.
The times on the left are for the stirred down starter and the right for the original starter. When the image was taken the stirred down starter had completely collapsed for some time.
After the starter was completely over fermented it was stirred down and allowed to re-ferment. It rose even higher than the original. This is possibly due to the the starter dough becoming more extensible. Just a guess.
This seems to refute the depleted food idea after maturity. There is also a thought that if the starter or dough is stirred or kneaded the microbes in the culture will come in contact with additional flour (carbs) because of the relocation of both substances. NOTE - I think mu buddy DocDough refutes that.
Thanks for posting this, Poldarn!
Danny
I don’t recall where I read this, but I do kind of remember the information.
The yeast & LAB can’t get around, on their own. So, they eat all the food-source that they can, right where they are. But, there is still unconsumed food in your mixture. When you stir your starter up, even if you don’t add more flour & water, it moves the yeast & LAB & leftover food-source into new positions, where they can begin to feed, again.
Volume is a terrible metric since it reflects retained CO2 which is a strong function of viscosity and materials properties (which reflects the history of mixing, temperature, flour, hydration, yeast and LAB specifics, etc).
I suggest that you use weight loss since CO2 initially saturates the dough and after the dough is saturated the CO2 escapes to the atmosphere (other than what remains trapped in the starter). And this goes on fairly uniformly for a long time. The best way to watch it is to use a high hydration mix and cover it with Stretch-tite which keeps water from evaporating while allowing CO2 to escape (and you can burp it before you weigh it to get rid of the excess if you want more accurate measurements). But you do need a scale that will give you pretty good accuracy. I use a scale with 1mg resolution, 5mg accuracy, and 120g capacity and a light weight container so that there can be 100g of starter at the beginning. This gives 5 parts in 1.2x10E6 absolute accuracy. When you track yeast activity this way you see that the weight follows a smooth sigmoid curve and continues for a lot longer than you expect. Stirring does not do much since at room temperature diffusion will move the nutrients around just fine and both yeast and LAB always grow faster in the direction of nutrient gradient so that they tend to maintain uniform nutrient density everywhere.