Have any of you made your own yeast from the air? Quoting: anonimalle
The only yeast recipes that I know of from air bourne yeast is sour dough and Amish Friendship Bread. The later used baking powder and baking soda as leaven substitutes, so that's cheating really.
An unusual bread that uses very little baking soda, but it troublesome to make well, and requires a knack, is salt-rising bread.
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I believe that what's happening is a collection of natural yeasts that add to the miniscule amount of baking soda. In a survival situation, or a time when ingredient availability was limited, you might be able to substitute the baking soda with wood ash.
I've been looking for alternative yeast recipes off and on for years. I think the idea is very cool to look for locally gathered materials for breads. While corn, acorn, cattail pollen, etc can be added to wheat, all yeasts need wheat components like gluten and natural "sugars" to activate it. That makes making bread in the absence of wheat very hard to produce a tasty loaf.
Many flatbreads can be produced using natural ingredients, but they just aren't as tasty by themselves, nor will these rise and make yummy texture like wheat bread that raises with yeast.