I tried an unleavened bread recipe that had me leave just flour, water, oil and salt at room temperature for 40 minutes. the person i was making it for said i had to throw it out because it was left too long and already had leaven in it. I have searched internet all day and can find no confirmation. They all say pretty much leave the flour/water mix 24 hours, throw out half, etc. I see in one of the comments here that the discard can be used as pancakes or pizza dough. Does that mean it has leaven in it at that point? Also does anyone know a site that might give specific info on the stages of development as far as when it is technically leavened even though it may not be a starter for bread? Fay, if you're talking about kosher/Passover dietary laws, your best bet would be to consult a site dealing with those issues; this site seems fairly easy to navigate, and gives leavening time as 18 minutes. Beyond that, scientifically speaking, the leavening process begins as soon as you combine yeast, flour, and water - it's pretty immediate. And yes, the starter has leavening agents – yeast – pretty much from the day it's started. Hope this helps - PJH

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