pkg. compressed or dry yeast

Yeast refers to single-celled fungi (Saccharomyces cerevisiae) cultivated and processed for leavening applications in baking and fermentation. Compressed yeast, also called fresh or cake yeast, is a moist, living culture typically containing 70% moisture, with a pale tan color and putty-like consistency; dry yeast is the same organism dehydrated to approximately 8% moisture and granulated for extended shelf stability. Both forms contain viable cells that ferment sugars, producing carbon dioxide gas and alcohol, thereby leavening doughs and batters. Active dry yeast granules are slightly larger and coarser than instant yeast (also called bread machine or rapid-rise yeast), which has been further processed to dissolve more quickly into dough.

Yeast is essential in breadmaking, where it ferments sugars in dough to create rise and develop flavor through complex chemical interactions. It is used in sweet doughs (brioche, cinnamon rolls), savory applications (focaccia, pizza), and historic fermented beverages (beer, wine, sake). In baking, yeast is typically bloomed or "proofed" in warm liquid before mixing into dough, or added directly to dry ingredients depending on the formula and yeast type. Fermentation duration ranges from hours to overnight, influenced by temperature, dough hydration, and desired flavor development. Compressed yeast requires refrigeration and shorter usage windows, while dry yeast offers convenience and longer shelf life, making it standard in home and commercial applications.