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For
starters
Ready to use yeast has not always been available. There were times
when bakers used to depend on airborne yeast to ferment their dough.
Whenever a batch of bread turned out well, a piece of its dough was set
aside and was used to ferment the next batch of dough. This portion of fermented
dough was known as a ‘starter’ for the next batch of dough. This procedure
is still used by some bakers to make certain types of bread. The bread made this
way is called sour bread. The same strain of yeast, used over a period of time,
imparts a certain flavor to the bread. This flavor is so peculiar to its
variety that experts can tell which part of the world a piece of sour bread has
come from.
Bakers
yeast
The yeast used for the bread available commercially nowadays is
called bakers yeast and is made specifically for baking bread and is
available both fresh and in a dried and powdered form. The carbon dioxide
produced by the yeast is driven away by heat during baking. The resultant holes
are what we see when we slice bread.
Brewers
yeast
Yeast is also used in the manufacturing of wine and beer. This
variety of yeast is known as brewers yeast. The yeast used for fermenting
wines occurs naturally in vineyards.
For
health and medicines
The addition of yeast enriches our diet as yeast is fifty per cent
protein and is also a rich source of several vitamins and other essential
nutrients. The credit for the usage and cultivation of yeast for the purpose of
baking and brewing goes to Louis Pasteur the French microbiologist.
Yeast has its medicinal uses too. It is used at certain stages during the
production of some antibiotics and steroids.
Dried yeast
Commercially available dried yeast is made by growing yeast cultures
in mediums that contain substances that encourage the yeast to multiply. When
the yeast is cultured to the right stage, the medium is discarded and the
resultant yeast is pressed into cakes with the help of a binding material.
During the process of brewing once the liquid to be fermented reaches the
desired level of fermenting, the yeast is removed and discarded. This discarded
yeast is used in the production of animal feed. |
