#leaven__leavening  a substance used to produce fermentation in dough or a liquid
  supertype:  #substance__matter  that which has mass and occupies space; "an atom is the smallest indivisible unit of matter"
  subtype:  #baking_powder  any of various powdered mixtures used in baking as a substitute for yeast
  subtype:  #sourdough  a leaven of dough in which fermentation is active; used by pioneers for making bread
  subtype:  #barm__yeast  a commercial leavening agent containing yeast cells; used to raise the dough in making bread and for fermenting beer or whiskey
     subtype:  #yeast_cake__yeastcake  small cake of compressed moist yeast
     subtype:  #brewer's_yeast  yeast used in fermenting beer
     subtype:  #mother.barm  a stringy slimy substance consisting of yeast cells and bacteria; forms during fermentation and is added to cider or wine to produce vinegar

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