Sourdough starter

A maintained mixture of flour and water containing wild yeasts and lactic acid bacteria. It ferments dough, producing carbon dioxide, acids, and flavor compounds.

Wild yeast: Yeasts that occur naturally in environments and foods rather than being introduced as a selected commercial strain. These yeasts produce carbon dioxide that raises dough in a starter.
Flour: A powder made by grinding cereal grains, roots, or other seeds. Flour supplies starch, minerals, and microorganisms’ other nutrients.
Sourdough bread: Bread leavened with a fermented flour-and-water culture rather than relying solely on commercial baker’s yeast. Starter is the leaven and fermentation source used to make it.
Ancient Egyptian bread: Bread made in ancient Egypt, where archaeological evidence includes early leavened loaves. Ancient leavened bread provides historical context for fermentation-based baking.
Baker’s yeast: Cultivated strains of Saccharomyces cerevisiae used to ferment dough and other foods. Commercial baker’s yeast leavens dough without the mixed microbial culture typical of starter.
Lactic acid bacteria: A group of bacteria that ferment sugars primarily into lactic acid and other products. These bacteria acidify starter and contribute characteristic sour flavors.
Water activity: A measure of the water available for microbial growth and chemical reactions in a material. A starter’s hydration affects which organisms can grow and how quickly.
Bulk fermentation: The first fermentation of mixed bread dough before it is divided and shaped. Starter activity drives dough expansion and flavor development during this stage.
Louis Pasteur: A French chemist whose research established microorganisms’ roles in fermentation and disease. His fermentation research helped explain the biological activity behind sourdough.
Chemical leavening: The release of carbon dioxide through chemical reactions in dough or batter, commonly using baking soda or baking powder. It raises baked goods without a living starter or microbial fermentation.

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