éleszt

Éleszt, commonly referred to in English as yeast, denotes a group of unicellular fungi that drive fermentation in bread, beer, wine, and other foods. The most important species for industry is Saccharomyces cerevisiae, used in baking and brewing. Other notable yeasts include Saccharomyces pastorianus, for lager beer, and Saccharomyces boulardii, used as a probiotic in some supplements.

Biology and life cycle: Yeasts are eukaryotic microorganisms that reproduce mainly by budding. They can grow aerobically or fermentatively, depending on oxygen availability. When oxygen is limited, they metabolize sugars to ethanol and carbon dioxide, a process that underpins leavening and alcohol production. Yeasts require nutrients, such as glucose, nitrogen, and minerals, to thrive.

Applications: In baking, yeast fermentation creates dough rise and flavors. In brewing and winemaking, sugars are converted to alcohol and CO2. Yeast is also used in bioethanol production and as a model organism in molecular biology, with the genome of S. cerevisiae among the first eukaryotic genomes sequenced.

Production and handling: Commercial yeast is cultured in sterile tanks, harvested, and dried or frozen for storage. Dry yeast and fresh yeast differ in shelf life and rehydration needs; when used in recipes, yeast is typically mixed with warm water and sugar to activate.

Safety and health: Yeast used in food processing is generally considered safe. Some yeasts, notably Candida species, can cause opportunistic infections in susceptible people, but baker’s or nutritional yeasts used in food are typically safe for healthy individuals.

History: The role of yeast in fermentation has been known since ancient times. In the 19th century, Louis Pasteur showed that living organisms, not chemistry alone, drive fermentation, a milestone in microbiology.