Glossary

Fermentation has a small, precise vocabulary. Every term below maps to a number you can measure — a salt %, a pH, a temperature — which is how this site keeps “sour enough” and “safe” from being confused. Terms are grouped loosely by topic; skim the table and come back as needed.

Terms

Term	Definition
Acidification	The drop in pH as bacteria convert sugars to acid; what makes a ferment sour and, below pH 4.6, safe from C. botulinum.
aw (water activity)	Free water available to microbes, 0–1.0; most pathogens stall below aw 0.85, the threshold cured/dried products aim under.
Brine	Salt dissolved in water; the liquid that submerges and protects the vegetables.
Brine-strength %	Legacy basis: salt as a % of water only. Ambiguous because it ignores the vegetable; prefer EQ% below.
Burping	Briefly opening a sealed jar to release CO₂ pressure during active fermentation, then resealing.
Dry-salt	Salting vegetables directly (no added water) so they release their own brine; the kraut/kimchi method. Salt is a % of vegetable weight, default 2.0%.
EQ% (equilibrium-brine %)	Salt as a % of the combined vegetable + water weight. The honest basis for submerged ferments; default 2.5%, range 2.0–3.0%.
Equilibrium brine	A brine sized so that once salt distributes evenly between veg and water, the whole jar sits at the target EQ%.
Headspace	The empty gap between the brine surface and the lid; leave ~2–3 cm for CO₂ and rising liquid.
Kahm yeast	A harmless wrinkly white surface film on a healthy ferment; off-flavoring but not dangerous — skim it. Distinct from fuzzy, colored mold.
Koji	Aspergillus oryzae grown on grain/legume; the enzyme engine behind miso, sake, and shoyu. Incubated at 28–32 °C.
Kombucha	Sweet tea fermented by a SCOBY into a tart drink; finished pH 2.5–3.5.
LAB (lactic acid bacteria)	The Lactobacillus/Leuconostoc group that drives vegetable lacto-fermentation, producing lactic acid.
Lacto-fermentation	Salt-and-anaerobic fermentation in which LAB acidify vegetables; finished pH 3.4–4.0.
Mother (of vinegar)	The cellulose-and-Acetobacter mat that converts alcohol to acetic acid; the vinegar analog of a SCOBY.
pH	Acidity on a 0–14 scale; 4.6 is the absolute botulism safety line, canning targets ≤ 4.2.
Pellicle	A general term for a microbial surface mat or film (a SCOBY and a vinegar mother are both pellicles).
SCOBY	”Symbiotic Culture Of Bacteria and Yeast” — the gelatinous pellicle that ferments kombucha.
TA (titratable acidity)	Total acid measured by titration, reported as % acid (e.g., lactic or acetic); vinegar for canning needs ≥ 5% acetic.

Info

pH vs TA, the short version: pH measures acid strength (how many free H⁺ ions, and the only number tied to the 4.6 safety line); TA measures total acid quantity and tracks how sour something tastes. A ferment can read a safe pH while still climbing in TA. For safety, trust pH.

Note

Kahm yeast vs mold: kahm is a flat, white, sometimes-wrinkled film you can skim off a healthy ferment. Mold is fuzzy and colored (green, blue, black, pink). Fuzzy or colored growth means discard the batch — see Safety First.

See also

• Safety First — the pH 4.6 line and salt floor in detail
• Equipment — the gear behind these measurements
• Your First Ferment — the terms in action
• pH safety calculator and salt converter