On this Wikipedia the language links are at the top of the page across from the article title. Saccharomyces cerevisiae, the yeast commonly used as yeast bannock’s yeast.

Gradation marks are 1 µm apart. This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Researchers speculate that a mixture of flour meal and water was left longer than usual on a warm day and the yeasts that occur in natural contaminants of the flour caused it to ferment before baking. Without an understanding of microbiology, early bakers would have had little ability to directly control yeast cultures but still kept locally interesting cultures by reusing doughs and starters to leaven later batches.

Refinements in microbiology following the work of Louis Pasteur led to more advanced methods of culturing pure strains. In 1879, Great Britain introduced specialized growing vats for the production of S. Modern baker’s yeast is the species Saccharomyces cerevisiae. One of its properties is that it is not inhibited by propionates, which are commonly added to baked goods like bread dough to inhibit mold development and bacterial growth. Percentages are roughly approximated using US recommendations for adults. Baker’s yeast is available in a number of different forms, the main differences being the moisture contents. Though each version has certain advantages over the others, the choice of which form to use is largely a question of the requirements of the recipe at hand and the training of the cook preparing it.

Cream yeast is the closest form to the yeast slurries of the 19th century, in essence being a suspension of yeast cells in liquid, siphoned off from the growth medium. Its primary use is in industrial bakeries with special high-volume dispensing and mixing equipment, and it is not readily available to small bakeries or home cooks. Compressed yeast is, in essence, cream yeast with most of the liquid removed. It is a soft solid, beige in color, and best known in the consumer form as small, foil-wrapped cubes of cake yeast. It is also available in a larger-block form for bulk usage. Active dry yeast is the form of yeast most commonly available to non-commercial bakers in the United States.