[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.

As always with our Cook the Book feature, we have five (5) copies of Mastering Fermentation to give away this week.

About the author: Kate Williams is a freelance writer and personal chef living in Berkeley, CA. She is a contributor to The Oxford American, KQED's Bay Area BitesBerkeleyside NOSH. Follow her @KateHWiliams.


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