Fermented Condiments

Why this method

Mustard, relish, salsa, and ketchup are all the same move: take a vegetable or seed base, let lactic-acid bacteria sour it at 2-3% salt, then season to taste after the ferment. The acid the bacteria produce gives a brightness and a clean tang that a vinegar-only condiment doesn’t have, and it keeps the condiment safe in the refrigerator. These are fresh, refrigerated condiments by default — they are not canned goods unless you follow a tested acidified-foods recipe and verify the pH.

Parameters

Parameter	Value
Salt	2-3% by weight (of the base)
Temperature	18-22 °C / 64-72 °F
Ferment duration	3-10 days (shorter for chopped fresh ferments)
Finished ferment pH	3.4-4.0 (meter-verified)
Storage	refrigerate at 2-4 °C

The four condiments

Info

The pattern is identical: ferment the base under brine or in its own salted liquor, then finish. Only the base and the final seasoning change.

Condiment	Base to ferment	Ferment	Finish with
Mustard	mustard seeds soaked in 2.5% brine	5-10 days	blend with vinegar, honey, spices
Relish	chopped cucumber/pepper/onion, 2.5% EQ brine	3-7 days	drain, season with vinegar, dill, sugar
Salsa	tomato, onion, chili, 2-2.5% salt	2-5 days	cilantro, lime, salt to taste
Ketchup	tomato base, 2% salt (often with a whey or brine starter)	3-7 days	reduce gently, vinegar, sweetener, spice

Workflow

Weigh and salt the base

Weigh the chopped vegetables or seeds. Add 2-3% salt by weight, or pack under a 2.5% equilibrium brine if the base won’t release enough of its own liquid. Use the dry-salt or brine salinity calculator for grams.

Ferment submerged

Pack into a jar with all solids under the liquid, weighted, with 2-3 cm headspace. Hold at 18-22 °C / 64-72 °F and burp daily if sealed. Chopped ferments move fast — taste from day 2.

Test and chill

When pleasantly sour, confirm pH 3.4-4.0 with a calibrated meter, then refrigerate. Cold storage at 2-4 °C slows the bacteria to a crawl and holds the texture.

Season after fermenting

Finish to taste cold — vinegar, sweetener, herbs, citrus. Adding acid (vinegar, lime) only lowers pH, which is safe; adding low-acid ingredients (fresh garlic, honey, water) can raise it, so re-measure if you plan to store the finished condiment unrefrigerated.

Caution

These recipes are for refrigerated condiments. Do not water-bath or pressure can a fermented condiment unless you follow a laboratory-tested process — ketchup, salsa, and relish often contain low-acid ingredients (onion, garlic, pepper) and a tested recipe balances the acid so the jar finishes at pH at or below 4.6 (canning target 4.2). Never cut the acid or salt in a canning recipe to suit taste. For tested salsa and relish recipes refer to NCHFP and the USDA Complete Guide to Home Canning.

Tip

Reduce fermented ketchup over low heat only — a hard boil drives off the volatile acids and dulls the lacto brightness you fermented for. Reduce gently, then re-balance with a splash of vinegar at the end.

Note

A spoonful of brine from an active sauerkraut or pickle jar, or a little whey, seeds the ferment with LAB and speeds the early acid drop — useful for low-sugar bases like mustard seed and tomato.

See also

• Fermented Hot Sauce · Fermented Pastes
• Lactic Fermentation · Sugar in Fermentation · Acidity and pH
• Safety First · Safety and Botulism
• Calculators: brine salinity · dry-salt · pH safety