Bassinage is an advanced mixing technique that involves holding back a significant portion of the water (typically 10–20%) from the initial mix and adding it slowly after the gluten network has already been developed. It is the secret weapon used to achieve modern "open crumb" sourdough (like Pan de Cristal).

Hydration Percentage in baking is a calculation that represents the ratio of water to flour in a recipe by weight. In sourdough, it is the primary variable controlling crumb openness.

Maltose is a disaccharide (simple sugar) produced when amylase enzymes break down the starch in flour. It is the primary fuel source for the sourdough ecosystem. Uniquely, the bacterium F. sanfranciscensis prefers maltose over glucose, giving it a competitive advantage in wheat dough.

Protease is a naturally occurring enzyme that breaks down proteins (proteolysis). In bread dough, protease degrades the gluten network over time.

Acetic acid is an organic acid produced by heterofermentative bacteria (like F. sanfranciscensis) alongside lactic acid, ethanol, and CO₂. It is responsible for the sharp, vinegary "tang" associated with San Francisco-style sourdough. Beyond flavour, it is a powerful antifungal agent.

Pre-shaping is an intermediate step between bulk fermentation and final shaping. The dough is divided and loosely formed into rounds, then left to rest (bench rest) for 15–30 minutes. This step reorganises the gluten network after the division and creates a smooth "skin" on the dough.

Refined Flour (often labelled as White Bread Flour) has had the bran and germ mechanically removed, leaving only the starchy endosperm. While this creates a flour that produces high volume and airy bread (due to strong, uninterrupted gluten), it is a biological "desert."

Hooch is a colloquial term for the liquid layer (ranging from clear to grey or black) that accumulates on top of a neglected sourdough starter. Biologically, it is primarily ethanol (alcohol) produced by wild yeast during fermentation.

Crumb Structure refers to the pattern of holes (alveoli) inside the bread. It is the primary diagnostic tool for a baker. A "tight" crumb with small, even holes often indicates lower hydration or over-handling. An "open" crumb with large, irregular holes indicates high hydration and gentle fermentation.

Wild Yeast refers to the diverse populations of yeast species found naturally on the husks of grain, in the air, and on the skin of fruits, which are "captured" and cultivated in a sourdough starter.

Lactic acid is an organic acid produced by Lactic Acid Bacteria (LAB) during the fermentation of carbohydrates. It is responsible for the mild, creamy, yogurt-like acidity in sourdough bread. It lowers the pH of the dough, activating enzymes and extending shelf-life by inhibiting mould growth.

Scoring is the act of cutting the surface of the proofed dough with a sharp blade (lame) immediately before baking. While often decorative, its primary function is mechanical: it creates a weak point for steam to escape.

Stone Ground Flour is milled by crushing grain between two stones. Unlike modern roller milling, which efficiently separates the bran and germ from the endosperm, stone milling crushes the entire berry together. Even if sifted later, the oils from the nutrient-rich germ are rubbed into the flour.

Inoculation Rate is the percentage of starter added to a dough relative to the total flour weight. For example, adding 200g of starter to 1000g of flour is a 20% inoculation. This variable acts as the "accelerator pedal" for fermentation.

Amylase is an enzyme naturally present in flour (and saliva) that acts as a biological catalyst. Its primary function is to break down complex starches (polysaccharides) into simple sugars (maltose and glucose).

Oven Spring is the rapid expansion of the dough that occurs during the first 10–12 minutes of baking. It is caused by the sudden thermal expansion of gases (CO₂) and the evaporation of water into steam within the dough. It stops once the crust hardens (sets) or the internal temperature kills the yeast (approx. 60°C).

GAD (Glutamate Decarboxylase) is an enzyme produced by certain strains of Lactic Acid Bacteria (such as L. brevis) within a sourdough starter. It facilitates the conversion of glutamate into GABA (Gamma-aminobutyric acid), a neurotransmitter associated with reducing anxiety and stress.

Gluten is a composite protein formed when two smaller proteins found in wheat—gliadin and glutenin—bond together in the presence of water and agitation.

Bulk Fermentation is the first rise of the dough, occurring after the starter is mixed in and before the dough is divided and shaped. It is named "bulk" because the entire batch of dough ferments as one mass.

While the terms are often used interchangeably, a "Starter" (or Mother) is the perpetual culture you maintain in a small jar, fed daily to keep it alive. A "Leaven" (or Levain) is an offshoot of that starter.