Onion in the Mother

A friend asked me the other day what she could do to increase the flavor and sourness of her sourdough breads. I told her: Add a piece of onion. My friend keeps what is called a 'sourdough mother' or simply a 'mother'. Other things in the cooking world use this type of nucleus to create a larger product and they are also called 'mothers', vinegar has 'mothers' for example. Perhaps it has to do with the nature of sour. For sourdough it's 'mother' is nothing more than a jar filled with a partially fermented flour and water paste. In 'Chef-World', it is known that adding a peice of raw onion to this mixture helps develop the flavor, this can be added to the mother or the off-spring but will have to be exchanged occaisionally with fresh pieces.
She uses a part of this paste each time she wants to make bread. Why this mixture works to leaven the bread is that the mother contains thousands of naturally occuring yeasts and bacterias. When they are fed with water and sugar (sugar in the form of flour), they eat and burp. This burp is the gas that causes the dough to puff up. When my friend puts her dough in the oven, the yeasts and bacteria die (which is why it stops rising). And about that onion: it is perhaps a wive's tale or a magic trick. I'll let my friend report back to us on how the onion wedge works.