Lieviti

Lieviti (sing. lievito) are a group of unicellular fungi, most notably Saccharomyces cerevisiae, used as leavening agents and in fermentation. In baking, these yeasts metabolize simple sugars to produce carbon dioxide and alcohol. The release of CO2 creates gas bubbles that cause dough to rise and develop texture and flavor during fermentation and baking.

Commercially, the term encompasses several forms: lievito di birra fresco and lievito di birra secco (active dry or fresh yeast), instant dry yeast (lievito secco istantaneo). There is also lievito madre, a natural sourdough starter maintained by regular feeding; it contains wild yeasts and lactic acid bacteria that contribute to leavening and acidity.

Beyond baking, yeasts are essential in brewing beer, winemaking, and other fermentation processes. They are used in biotechnology to produce ethanol, enzymes, and other products.

Growth conditions and handling are important for performance: optimum temperature is around 25-30°C; high sugar or salt, drying, or acidic pH can inhibit growth. Fresh yeast lasts about 1-2 weeks refrigerated, while dry forms have longer shelf lives when stored cool and dry. Yeasts are living organisms, and their activity can be affected by temperature, osmotic stress, and alcohol concentration.

In culinary contexts, lievito madre is valued for flavor and texture development in artisan bread, while commercial yeasts provide reliable and rapid leavening for a wide range of baked goods and fermented beverages.