Yeast

Yeast

SACCHAROMYCES CEREVISIAE
Kind: Additive, leavening agent

Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom.

Yeast, the most common one being S. cerevisiae, is used in baking as a leavening agent, where it converts the food/fermentable sugars present in dough into the gas carbon dioxide. This causes the dough to expand or rise as gas forms pockets or bubbles. When the dough is baked, the yeast dies and the air pockets “set”, giving the baked product a soft and spongy texture. The use of potatoes, water from potato boiling, eggs, or sugar in a bread dough accelerates the growth of yeasts. Most yeasts used in baking are of the same species common in alcoholic fermentation. In addition, Saccharomyces exiguus (also known as S. minor), a wild yeast found on plants, fruits, and grains, is occasionally used for baking. In breadmaking, the yeast initially respires aerobically, producing carbon dioxide and water. When the oxygen is depleted, fermentation begins, producing ethanol as a waste product; however, this evaporates during baking.

Source Wikipedia

50 g fresh yeast = 4 tsp dry yeast

Fresh Yeast
Fresh yeast is hard to find in some countries. In England you can sometimes buy (or even get some) from the bakery in superstores like Asda or Tesco. You can froze yeast if you manage to get hold of more than you need for your bread. Take out from the freezer the night before and let slowly thaw. It might end up being a bit runny, but usually works fine anyway.
Dry Yeast


The Saccharomycetaceae Family

A family of yeasts


Kingdom: Fungi   Phylum: Ascomycota   Class: Saccharomycetes   Order: Saccharomycetales