Leavening

n.	1.	The act of making light, or causing to ferment, by means of leaven.
	2.	That which leavens or makes light.

Noun	1.	leavening - an influence that works subtly to lighten or modify something; "his sermons benefited from a leavening of humor" Synonyms: leaven
	2.	leavening - a substance used to produce fermentation in dough or a liquid Synonyms: leaven

baking powder, barm, leaven, matter, sourdough, substance, yeast