gjæren

Gjæren, in Norwegian, refers to yeast, a group of single‑celled fungi, most commonly Saccharomyces cerevisiae, used in baking, brewing, and other fermentation processes. Yeast cells metabolize sugars and produce energy through fermentation, yielding carbon dioxide and ethanol. This biochemical activity is what causes dough to rise in baking and drives alcoholic fermentation in beverages.

In baking, baker’s yeast is added to dough and activated by warmth and moisture. The produced carbon dioxide forms bubbles that expand the dough, giving bread its light texture. In brewing and winemaking, yeast converts fermentable sugars in wort or must into alcohol and carbon dioxide, shaping the flavor, aroma, and strength of the final product. Different yeast strains are selected for specific traits, such as gas production, aroma, temperature tolerance, and sugar utilization.

Yeast exists in several forms. Fresh yeast comes as a moist, perishable block, while active dry yeast and instant yeast are dried forms with longer shelf life. Nutritional yeast, a deactivated form, is used as a food supplement. Industrial production of baker’s yeast involves controlled fermentation, harvesting, and processing the cells into usable products. Storage requirements vary by form; cooled environments extend viability, and rehydration or proofing may be recommended before use.

Historically, yeast domestication and use in fermentation date back thousands of years, with significant advances in microbiology and industrial production occurring in the 19th and 20th centuries, notably through the work of scientists such as Louis Pasteur. Today, gjæren is a central tool in food and beverage production, valued for its reliability, efficiency, and diverse applications. It is generally safe for consumption, though individuals with yeast allergies or intolerances should avoid products containing active yeast.