Tomato Ketchup from 'Mastering Fermentation'

Fermented Tomato Ketchup
Photograph: Ed Anderson

Would you ever think of making fermented ketchup? I certainly hadn't before pickling up my copy of Mary Karlin's new cookbook, Mastering Fermentation. Yet, after pondering the history of the condiment, it makes a lot of sense. Ketchup has its roots in Southeast Asian kecap manis, which, as a sweet soy sauce-relative, is usually fermented to a certain degree. Karlin's ketchup is definitely American, though. It's a simple mixture of tomato paste, salt, Worcestershire (if you're really ballsy, you could make your own), raw honey, and a starter culture, and it only needs a couple of days to get all bacteria-fied.

Why I picked this recipe: I've made homemade ketchup before, but I've never fermented it.

What worked: This recipe was hands-down the easiest ferment I've ever made and it definitely tasted more interesting than the store-bought stuff.

What didn't: I ended up putting the ketchup in two smaller jars and let one ferment an extra 8 hours or so. I thought the extra time mellowed out the flavor of the tomato paste, and found this batch much better than the one following Karlin's suggested timeline.

Suggested tweaks: This is a bare bones recipe, so you could add just about any spice or additional seasoning you'd like. Karlin suggests red pepper flakes, cayenne, or smoked paprika. (My vote is definitely for the smoked paprika.) I used water kefir (recipe coming later this week) as a starter, but I'm sure whey from good quality store-bought yogurt would work well if you don't have any other ferments going.

Reprinted with permission from Mastering Fermentation: Recipes for Making and Cooking with Fermented Foods by Mary Karlin. Copyright 2013. Published by Ten Speed Press, an imprint of the Crown Publishing Group, a division of Random House. All rights reserved. Available wherever books are sold.

Recipe Facts

Active: 20 mins
Total: 60 hrs
Makes: 1 quart

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  • 3 cups canned or homemade tomato paste
  • 2 teaspoons unrefined fine sea salt
  • 1/4 cup Worcestershire sauce
  • 1/2 cup raw, unfiltered apple cider vinegar
  • 6 tablespoons robust flavored raw, unfiltered honey such as clover, or organic amber maple syrup
  • 1/4 cup basic whey (from yogurt), water kefir, or vegetable brine (such as from sauerkraut), as fermenting agent


  1. Combine all the ingredients in a bowl, making sure the salt and the honey are dissolved. Transfer to a wide-mouth 1-quart jar. Secure a piece of cheesecloth to the opening and allow to sit at room temperature for 8 hours or overnight. Remove the cheesecloth and secure an airtight lid. Refrigerate for 2 days before using. Use within 2 months.