What exactly happens during the sourdough ripening?

Question

I am following a recipe from the well established Italian Baker Bonci, to make my liquid sourdough starter (with some success too).

In his recipe he says to refresh the starter with a 1:1:1 proportion every day for a month before it can be considered matured and ready to use.

I would like to know what happens during these 31 days and why this time frame is needed (the starter seems very active after a week or two and is capable of leavening bread already).

My understanding /theory is that the successive rounds of feeding, souring and re feeding help grow yeasts while acidity weeds out some of them, in fact selecting the right "genes" we want to keep in our starter.

I would like to know :

1. If my theory is correct and if it is
2. Exactly what traits/type of yeasts are we selecting for?
3. What are the typical proportion of a yeast types found in starter?
4. Is there any source describing the detail of this process (I'm interested in the selection part more than in the recipe part, but I don't won't a bio textbook)

Answer 1

Here is a small piece of the answer. https://pubmed.ncbi.nlm.nih.gov/33496265/ It is not just yeast strains but especially lactobacillus bacteria that develops and helps to change the ph of the starter. This change in ph is what helps the sourdough bread retain moisture and results in the creation of acetic and lactic acids which create the tanginess.

Answer 2

You dont need to wait a month to use it. I really do get very unhappy when I see cooks discarding starter culture. After a week you can start adding it to pretty much any baked good to improve it.

You need about 3 weeks of yeast cultivation before your starter can levain a bread but after a week you can use it in pancakes, muffins, or scones and it will improve it. Sourdough pancakes is high art.

Dont ever throw starter away. It is much too precious.

You dont quite realise how great a cheapening effect mass produced yeast has on baked good until you start harvesting your own. I found it helped my indigestion greatly.

It is probably good for for the same reason pickling juice is considered good for you in certain parts of Europe.