What is the science behind sourdough? How are ‘starters’ usually so many years old?

Question

What is the science behind sourdough? How are ‘starters’ usually so many years old?

In: Other

Answer 1

yeast is in the air all around you. When you make a new sourdough starter, the ambient yeast gets into the dough. You keep feeding that yeast and it grows making more yeast. As long as you keep feeding it, it keeps growing.

Then you can share the starter just by ripping off a bit of dough with the yeast cultures in it.