Tomato Catsup (Ketchup), Lacto-Fermented

Homemade Ketchup

Homemade Ketchup

by Cat, April 2010 (photo, right, from Wikimedia Commons)

Back in the days before refrigeration and modern canning, summer’s bounty was preserved by lacto-fermentation. Perhaps the most well known of these is sauerkraut. Next to salsa, ketchup is the most used condiment in America; in those older times, it too was lacto-fermented, but today it is little more than tomato-stained HFCS.

Just imagine what the real ketchup tasted like! Rich with the flavors of ripe tomatoes and other fruits & vegetables, and a bit of fish sauce (or anchovy paste), with a sweet-tart tang. Well, imagine no more. Try making your own!

See also: 1. Homemade Tomato Paste; 2. Condiments (menu); 3. Misc. Information (menu: scroll down to ‘Lacto-Fermentation’); 4. Salsa Verde, Lacto-fermented

Experiment with other richly-flavored ingredients, such as capers, brined olives, or mushrooms, ground to a paste and added to the tomato mix.

In addition to ketchup, you can also make lacto-fermented salsas and other vegetable ferments & condiments, using tomatoes and its cousins like peppers and tomatillos.

Tomato Catsup (Ketchup)

This recipe is adapted from Nourishing Traditions, by Sally Fallon (1), and Edible (2). Check out the Edible Aria recipe page, as it includes an old catsup recipe from the First African American Cookbook, 1881.

You can start with commercial tomato paste, but since most cans are lined with BPA (Muir Glen’s cans are lined with a type of ceramic), and you can never be sure there aren’t hidden ingredients not listed on the label, I prefer to make my own tomato paste.

Feel free to experiment with adding other fruits/veggies. For example, bell peppers or mildly-spicy peppers, peaches, plums, scallions, onions, ginger.

You can also experiment with spices such as allspice (aids in preservation as well as adds flavor), cloves, coriander, cardamom.

I’m not a fan of fish sauce, so I use anchovy paste. Both are fairly salty so you may need less salt. Start out with half the amount and then taste.

You will note that no vinegar is used. That is because the probiotics in the whey, acting on the sugars in the tomatoes and maple syrup/molasses, produce lactic acid which is tart. This process is called lacto-fermentation, and acts to preserve the Ketchup without canning. Once fermented, the catsup should be stored in the fridge or other cold storage.

Makes 1 quart.

Ingredients & Equipment:

  • 3 cups tomato paste (preferably homemade or Organic)
  • 3 cloves garlic, peeled, minced & mashed to a paste with ½ tsp of the salt
  • 1 Tbsp Unrefined sea salt, or less if using fish sauce
  • ¼ cup liquid from another lacto-fermentation product (or ½ tsp culture starter mixed with a few Tbsp water)
  • ½ cup maple syrup or 2 Tbsp molasses
  • ¼ tsp cayenne pepper or to taste
  • ½ tsp black pepper
  • ½ cup fermented fish sauce, or 2 – 4 whole anchovies, or  1 – 2 tsp anchovy paste
  • Equipment
  • bowl
  • immersion blender, whisk or manual blender
  • food mill (optional); see photo, below
  • quart mason jar for fermenting; half-pint or pint jars for storing.

* Instead of whey, you could use juice from another fermentation such as lacto-fermented sauerkraut. The probiotics are necessary to combat the growth of undesirable bugs so I don’t recommend using (just) lemon or lime juice.


  1. Combine all ingredients in a bowl and blend with an immersion blender or other implement. If not completely pureed, use a food mill (pictured below, from Wikimedia Commons)
  2. Place in wide-mouth mason jar; the top of the mixture should be at least 1 inch below the top of the jar.
  3. Leave at room temperature for 2 – 3 days (to desired level of tartness), then transfer to fridge. I like to transfer to smaller jars for storage, as I don’t use it up very fast.
Food Mill (Moulinette)

Food Mill (Moulinette)

(Photo from Wikimedia Commons)


  1. Nourishing Traditions,

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