/ 50 g yeast

Yeast refers to single-celled fungi of the genus Saccharomyces, most commonly Saccharomyces cerevisiae, which are used extensively in food production and fermentation. These microorganisms are naturally present on fruit skins and in grain environments, though commercial yeast is cultivated in controlled conditions and supplied in various forms: fresh (compressed), active dry, or instant. Yeast converts sugars into alcohol and carbon dioxide through fermentation, a metabolic process that has been exploited for thousands of years in baking and brewing. The organism is characterized by its ability to survive in anaerobic conditions and its sensitivity to temperature, with optimal fermentation occurring between 70-78°F (21-26°C) for most baker's yeasts.

Different strains exhibit varying fermentation rates and flavor profiles; baker's yeast (S. cerevisiae) produces rapid, clean fermentation suitable for bread-making, while brewer's yeast and wild yeasts develop more complex flavors in beer and wine production. The cellular composition of yeast includes proteins, B vitamins, and minerals, making it nutritionally significant beyond its leavening function.

Yeast is indispensable in baking, where it produces carbon dioxide gas that leavens dough, creating the crumb structure in breads, pastries, and cakes. In bread-making, yeast fermentation develops flavor compounds and strengthens gluten networks through enzymatic activity. Beyond baking, yeast is central to brewing beer, fermenting wine, and producing other fermented beverages and foods such as kombucha and miso. The fermentation process also occurs in sourdough starters, where wild yeast and lactic acid bacteria create naturally leavened breads with distinctive tangy flavors. Yeast is also employed as a nutritional supplement in the form of nutritional yeast, which provides umami flavor and B vitamins to savory dishes, soups, and vegan preparations.