Hooch

Hooch is the informal name for the grayish-black or dark brown liquid that separates and floats on the surface of a sourdough starter that has not been fed for an extended period. Its formation is a straightforward consequence of microbial metabolism: the wild Saccharomyces cerevisiae and non-Saccharomyces yeasts in the starter ferment available sugars, producing ethanol (alcohol) and carbon dioxide; simultaneously, lactic acid bacteria — primarily Lactobacillus sanfranciscensis (now reclassified as Fructilactobacillus sanfranciscensis) and related heterofermentative species — produce lactic and acetic acids. When the fermentable carbohydrates are fully consumed, yeast activity halts and the culture stratifies: the denser, more acidic paste sinks; the ethanol-and-water solution, being less viscous, rises to the top. The liquid is genuinely alcoholic (typically 1–4 % ABV in a very neglected starter) and sharply acidic. Hooch appearance tells the baker two things: the starter is hungry and the culture has shifted toward higher acidity, particularly acetic acid, which gives sourdough its sharp, tangy character. A starter showing hooch is not dead — the bacteria and dormant yeast remain viable — but if left too long in a very acidic, nutrient-depleted state, yeast populations decline and the culture weakens. To restore the starter, simply pour off or stir the hooch back in (stirring it in produces a more sour loaf; discarding it produces a milder one), then discard all but a small portion of the starter and feed with fresh flour and water at a 1:3:3 or similar ratio. The culture should show signs of activity — bubbles, dome, rise — within 4–12 hours at room temperature, depending on ambient temperature and culture health. Preventing hooch formation is largely a matter of regular feeding cadence: daily at room temperature, or weekly if the starter is refrigerated.

“After a week in the back of the fridge, the starter had developed a thin layer of hooch; she stirred it back in for a more assertive tang, discarded all but 50 g, and fed it twice before committing to the bake.”

• techniquesSourdough Starter Maintenance
• ConceptAcetic Acid Fermentation
• techniquesLevain Building

1. 1.Tartine Bread — Chad Robertson (Chronicle Books, 2010)
2. 2.The Rye Baker — Stanley Ginsberg (W. W. Norton, 2016)
3. 3.Modernist Bread — Myhrvold & Migoya (The Cooking Lab, 2017)
4. 4.Sourdough: Recipes for Rustic Fermented Breads — Sarah Owens (Roost Books, 2015)

Confidence: high