Fresh Yeast
I buy fresh baker's yeast from Morrison supermarkets. As most of the recipes I use only need 1g - 3g of yeast, I store it in cling film (1g units) in the freezer. When I need to make some bread, I remove the yeast from the freezer about 10 to 15 minutes before I bake. Most of my recipes use a sourdough starter and fresh baker's yeast.
Information on the sourdough starter can be found on the sourdough page.
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Yeasts can be considered man's oldest industrial microorganism. It's likely that man used yeast before the development of a written language. Hieroglyphics suggest that that ancient Egyptians were using yeast and the process of fermentation to produce alcoholic beverages and to leaven bread over 5,000 years ago.
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What is yeast?
Yeasts are single-celled fungi. As fungi, they are related to the other fungi that people are more familiar with. These include edible mushrooms available at the supermarket, common baker’s yeast used to leaven bread, moulds that ripen blue cheese and the moulds that produce antibiotics for medical and veterinary use. Many consider edible yeast and fungi to be as natural as fruits and vegetables.
Over 600 different species of yeast are known and they are widely distributed in nature. They are found in association with other microorganisms as part of the normal inhabitants of soil, vegetation, marine and other aqueous environments. Some yeast species are also natural inhabitants of man and animals. While some species are highly specialized and found only in certain habitats at certain times of the year, other species are generalists and can be isolated from many different sources.
Baker’s yeast is used to leaven bread throughout the world and it is the type of yeast that people are most familiar with. Baker’s yeast is produced from the genus and species of yeast called Saccharomyces cerevisiae. The scientific name of the genus of baker’s yeast, Saccharomyces, refers to “saccharo” meaning sugar and “myces” meaning fungus. The species name, cerevisiae, is derived from the name Ceres, the Roman goddess of agriculture. Baker’s yeast products are made from strains of this yeast selected for their special qualities relating to the needs of the baking industry.
The typical yeast cell is approximately equal in size to a human red blood cell and is spherical to ellipsoidal in shape. Because of its small size, it takes about 30 billion yeast cells to make up to one gram of compressed baker’s yeast. Yeast reproduce vegetatively by budding, a process during which a new bud grows from the side of the existing cell wall. This bud eventually breaks away from the mother cell to form a separate daughter cell. Each yeast cell, on average, undergoes this budding process 12 to 15 times before it is no longer capable of reproducing. During commercial production, yeast is grown under carefully controlled conditions on a sugar containing media typically composed of beet and cane molasses. Under ideal growth conditions a yeast cell reproduces every two to three hours.
Yeast is the essential ingredient in many bakery products. It is responsible for leavening the dough and imparting a delicious yeast fermentation flavour to the product. It is used in rather small amounts in most bakery products, but having good yeast and using the yeast properly often makes the difference between success and something less than success in a bakery operation.
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