Fermented Ketchup

Homemade condiments like fermented ketchup provide another way to take in probiotics, while at the same time eliminating another High-Fructose Corn Syrup-laden food from your diet. They are also a great way to sneak probiotics (good bacteria!) into your kids’ meals.

Bonus points if you make your own paste from fresh tomatoes. If you just don’t have the wherewithal or time to paste your own tomatoes (and it IS a long process!), it would be okay to use organic canned tomato paste. We won’t tell! 😉

Fermented Ketchup
Recipe type: condiment
Prep time: 
Fermentation time: 
Yield: 2 pints
  • 10 lbs. fresh San Marzano or other pasting variety tomatoes OR four 6 oz. (170g each) cans of organic tomato paste, totaling 24 oz/700g
  • ¼ cup/60 ml by volume or 3 oz/85g by weight honey
  • 2-3 garlic cloves
  • 6 fl. oz (180ml) olive or pickle brine, apple cider vinegar or very ripe kombucha (acidic liquid)
  • 2 teaspoons/10ml sea salt
  • 1 teaspoon/5ml clove, ground
  • 2 teaspoons/10ml allspice, ground
Make Paste (from scratch)
  1. Wash and remove stems from tomatoes.
  2. Make an "X" shaped slit in the skin of the tomatoes at the stem end.
  3. Boil water in a medium to large stockpot.
  4. A few at a time, drop the tomatoes in for 30-40 seconds. Fish out with a spider or slotted spoon.
  5. Immediately put them in a bowl filled with ice water. Then pinch the tomatoes from the non-slit end. The skins will pop off. Set aside in another bowl. Compost or discard skins.
  6. Cut tomatoes open and squeeze out gel and seeds. (Reserve for another use).
  7. Puree drained tomato flesh in a food processor until mostly smooth (a few lumps is okay).
  8. Pour contents into a slow cooker, and cook for 8-10 hours on low heat, stirring occasionally. During this time, most of the juice should evaporate off, and it will take on a darker color. It won't be as thick as canned tomato paste. You can cook longer if you want a thicker paste.
  9. Let paste cool.
Mix ingredients (Start here if using tomato paste)
  1. Peel and mince garlic finely, or grate using a microplane. Add to mixing bowl
  2. Add paste to a mixing bowl, along with honey. Stir until smooth.
  3. Add acidic liquid, ½ cup of brine or whey and salt, cloves and allspice to bowl.
  4. Stir contents well.
  1. Transfer to a quart mason jar or two pint jars.
  2. Cover tightly and let ferment at room temperature for 3 to 10 days.
  3. When you like the taste, transfer and store in refrigerator. Scrape down sides of jar to reduce chance of mold formation. Lasts at least 6 months.

8 thoughts on “Fermented Ketchup

  1. marykorte

    what do you do about the white stuff on the top? How long will this last in the fridge? How does the flavor compare to conventional ketchup?

    • Austin Post author

      The white stuff is dried whey. You can either mix it in or scoop it off. If there are any off-color spots (blue or black), that’s mold, and you should definitely scoop those off.

      I think it should last about 3 months in the fridge, tightly sealed.

      I think it’s a much more complex flavor, especially with the allspice/cloves combination. More tomatoe-y too!

    • Austin Post author

      Most ferments will work without whey (the whey gives it a “kick start”). I would add a few days to the fermenting time if you’re not using whey. Let us know how it goes!

      • Jen

        If I’m not using whey, the sea salt and vinegar will ferment the ketchup?

        • Jen

          Also, where should I buy the whey if I choose to use it? Jimbos?

        • Austin Post author

          Hi Jen,
          Yes, it should still ferment without whey. The whey gives the good bacteria a head-start on fermenting.

          Your best bet is to make your own liquid whey by straining out fresh yogurt or kefir. Here’s a good procedure: http://www.cheeseslave.com/how-to-make-whey/

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