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Fermented Tomato

Pomodoro Fermentato

Ripe tomatoes in 2.5 percent salt, fermented until they turn lactic and bright.

Fermented tomato among DUKAI pantry ferments, oils and preserves.

A bulk ferment built to give two things from one batch: a clear, acidic tomato liquor and a concentrated fermented flesh. The tomatoes are cut rather than pureed so the two can be separated at the end.

A bulk batch from 5 kg of tomatoes

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Salt is calculated on the prepared tomato weight, not taken from a fixed figure. Weigh what you actually have after trimming and multiply by 0.025. And do not add lemon juice or vinegar: the acidity has to come from the fermentation itself.

Chef Paul Dukai

Ingredients

  • Ripe tomatoes, firm and very fresh5 kg
  • Non-iodised sea salt, 2.5 percent of the prepared tomato weight125 g
  • Fresh garlic50 g
  • Fresh basil25 g
  • Coriander seed, lightly crushed5 g
  • Black peppercorns5 g

Method

Preparation

  1. Wash and inspect the tomatoes carefully, removing stems and any damaged fruit. Quarter the large ones and halve the medium ones. Do not puree them: enough structure has to remain for the flesh and the liquor to be separated later.

  2. Weigh the prepared tomatoes after trimming and calculate the salt at the tomato weight multiplied by 0.025. For 5,000 g of tomato that is 125 g of salt. Do not rely on a fixed salt quantity if the batch size changes.

  3. Put the tomatoes into a sanitised food-grade container with the salt and massage gently but thoroughly for 2 to 3 minutes, until the salt is evenly distributed and the tomatoes begin to release their own liquid. Leave for 30 to 60 minutes.

  4. Add the garlic, basil, coriander seed and black peppercorns.

  5. Transfer everything to the fermentation vessel and press the tomatoes down so their own liquid rises around them. They must stay submerged: use a fermentation weight, and an airlock is strongly preferred.

Fermentation

  1. Ferment in a controlled environment at 18 to 22°C. Because the tomatoes are cut, this is considerably more active than a whole-tomato batch, and the useful window is commonly 2 to 5 days.

  2. Day 1: look for slight bubbling, check the aroma, check that the tomatoes are still submerged, and measure the pH.

  3. Day 2: bubbling should be increasing and the tomato beginning to develop acidity. Measure the pH.

  4. Day 3: taste, looking for a clean lactic acidity. Measure the pH.

  5. Days 4 and 5: keep tasting and measuring, and stop when the flavour is where you want it.

  6. Readiness is not decided by the calendar. Fermentation guidance targets a pH below 4.6, with some vegetable-fermentation guidance recommending pH 5.2 or below within 24 hours and below 4.6 within 48. Measure rather than assume.

Separating the two products

  1. Once the ferment reaches the flavour you want, separate it. Pass through a fine chinois without pressing aggressively.

  2. What comes through is the fermented tomato water: clear, acidic and naturally umami, for brodos, dressings, seafood preparations and vinaigrettes.

  3. What stays behind is the fermented tomato flesh, a concentrated ingredient in its own right.

Chef’s notes

  • Two products, one batch, essentially zero waste. The water and the flesh are both this recipe: neither is a separate preparation, and neither needs making again.

Keeping

DUKAI storage guidance

Once the ferment is where you want it, refrigerate at 5°C or below to slow it, keeping everything submerged in its own liquor. Measured pH is the control, not a date: a finished ferment below pH 4.6 held cold keeps for weeks and goes on developing. Use clean utensils every time, and stop using a batch that smells wrong, has mould, or has risen above pH 4.6.

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Last refined · September 2026