Why stirring an over-fermented sourdough starter caused it to rise a second time to about double the original size? After feeding my sourdough starter, I let it rise to about 2.5x the original height. It eventually collapsed. 24 hours later, after it was well over fermented, I stirred the starter with a spoon. It then suddenly grew back to 2x in about 1 to 2 hours, without adding any water or flour. Can anyone explain this phenomenon?
You actually kneaded the dough. This puts some of the flour and water into contact with yeast that didn't have access to food cause it already ate all its sources within their grasp. Feeding these yeast cells this way caused the second rise, a common method in bread making.