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Yeast is a tiny single celled fungus which scientists refer to as a “microorganism”. This cell is shaped like an egg and can only be seen through a microscope as its size is no more than 6 to 8 thousandths of a millimetre.
The yeast is surrounded by a cellular wall which surrounds the cell membrane. This wall protects the yeast from damage and is comprised of:
- An outer layer of mannoproteins, combined with glucanes;
- An inner layer of glucanes combined with chitin;
- A cell membrane rich in protein complexes.
The autolysis of the cells, (a conversion process designed to concentrate them by various means) results in the production of yeast extracts which are rich in glutamates, glucans, nucleotides and vitamin B. Among other things, these are used in the preparation of cookery products, pharmaceutical preparations and culture mediums.
Saccharomyces cerevisiae
The best known variety of yeast is referred to as Saccharomyces cerevisiae: Saccharo for sugar and Myces for fungus. In Latin, the cerevisiae species means “brewery”.
This yeast is the one used for bread making. One of its special characteristics is its ability to transform the sugars naturally present in flour into alcohol (which is evaporated away during baking) and into carbon dioxide. It is this last aspect which gives the bread its overall volume.
