Man used yeast before he knew how to write.
Hieroglyphics suggest that the ancient Egyptian civilizations were using
living yeast and the process of fermentation to rise their bread
over 5,000 years ago. Of course, they didn’t know what was responsible
for the leavening process. The chemical action of yeast that causes dough
to rise is known as fermentation and was probably looked upon by early
man as a mysterious and unreal phenomenon. It is believed that since
early times, mixtures of leavening for bread making were formed by
natural contaminants of the four such as: wild yeast and lactobacilli
(organisms also present in milk). Leaven, mentioned in the Bible, was a
soft dough-type medium kept from one baking of bread to another. A
small portion of this dough was used to start or leaven each new bread
dough. Later scientific research found that yeast is a microorganism
(visible only with a microscope). The chemical action and growth of yeast
that caused the dough to rise then became understandable.
2. WHAT IS YEAST
Yeast is a tiny form of fungi scientists call microorganisms. They are egg-
shaped cells that can only be seen with a microscope. It takes 20,000,00
00,000 (twenty billion) to weight one gram or 1/28 of an ounce.
The scientific name for one species of yeast is SACCHAROMYCES
CEREVISIAE or sugar eating fungus. Cerevisiae is the Latin word for
brewer. A very long name for such a tiny organism. It is a very strong
strain that is capable of fermentation or causing bread dough to rise.
Yeast cells digest food to obtain energy for growth. Their favorite food is
sugar; sucrose (beet or cane sugar), fructose and glucose (found in
honey, molasses, maple syrup and fruit) and maltose(derived from starch
in flour). The process, alcoholic fermentation, produces useful end
products, carbon dioxide and ethyl alcohol, which are released by the
yeast cells into the surrounding liquid. This is how alcoholic drinks are
produced from starch containing flours, i.e., barley flour for making beer
and wheat, corn or other grains for making whiskey.
Fermentation occurs naturally in nature. For instance, many berries break
open in late fall when they are over-ripe and full of sugar. Natural yeast
from the air, so tiny they cannot be seen, lodge on the surface of these
berries, which then become fermented and alcoholic.
In commercial fermentation of grape juice for the production of wine, the
carbon dioxide gas escapes from the solution. Evidence of gas can be
seen in the heavy foam caps in fermenting wine tanks. In bread baking,
when yeast ferments the sugars available from the flour and from added
sugar, the carbon dioxide gas cannot escape because the dough is elastic
and stretchable. Therefore, the dough inflates as a result of the expanding
gas. Thus, the term yeast-leavened breads came into the vocabulary of
the world of baking.