Simple Lacto-Fermented Ketchup

Posted on Jan 21, 2013 in Blog, Fermentation, Recipes | 36 comments

Simple Lacto-Fermented Ketchup

My fascination with and passion for fermented foods seems to stop at nothing…including cultured condiments. A recent experiment with lacto-fermented ketchup has left me utterly in love with the stuff and uninterested in returning to its store-bought counterpart. Making lacto-fermented condiments is as simple as adding some fresh whey to the recipe and leaving the whole thing on the counter for a few days. The resulting flavors are complex, tangy, and satisfying. I’ve experimented with a few great lacto-fermented ketchup recipes, including one from Nourished Kitchen which I recommend if you like robust herbs like allspice & cloves.

The recipe below is my favorite, incorporating maple syrup which lends its characteristic caramel flavor & organic apple cider vinegar which gives the ketchup a nice tang. I also chose to use Muir Glen tomato paste since their cans are BPA-free. The whole fermentation process takes 3 to 5 days depending on your taste preferences, so don’t go grilling up those burgers just yet. But fear not, this ketchup is well worth the wait. So sit tight and plan several weeks to come worth of ketchup-enhanced meals!

Measuring the ingredients

Measuring the ingredients

Lacto-fermented Ketchup

Lacto-fermented Ketchup


Simple Lacto-Fermented Ketchup
  • 3 cans of Muir Glen tomato paste (6 oz. each) OR approximately 2 cups of tomato paste
  • ¼ cup organic maple syrup (other sweeteners like honey or organic sugar may be substituted)
  • ¼ cup fresh whey, plus 2 Tablespoons (divided)
  • 2½ Tablespoons organic, raw apple cider vinegar
  • 1 teaspoon sea salt
  1. Spoon the tomato paste into a mixing bowl & mix in the maple syrup.
  2. Next, stir in ¼ cup of the whey, cider vinegar, and sea salt until well-mixed.
  3. Spoon the mixture into a wide-mouthed glass quart jar. Do your best to smooth the top of the mixture so that it is as flat as possible.
  4. Pour the remaining 2 Tablespoons of whey on top of the ketchup.
  5. Cover the jar loosely with a lid and set it on the counter for 3 to 5 days. When ready, give it a stir before refrigerating to allow some of the air bubbles (a byproduct of the lacto-fermentation) to escape.

Pretty easy, huh? Like other vegetable ferments, this recipe should keep well in your fridge for several months, just like the store-bought kind, but without any suspicious preservatives. My favorite way to eat it is atop homemade bean burgers. Let me know how yours turns out!

In the jar & ready to sit for 3 to 5 days

In the jar & ready to sit for 3 to 5 days


Resources for this recipe:


  1. Do you know of any other canned food companies that are bpa free?

  2. What is whey?

    • Whey is the liquid remaining after curdled milk or yogurt has been strained. In the case of yogurt, it contains lots of probiotic bacteria which can jump start the lacto-fermentation process.

      • the curdled milk and its whey dosnt contain lots of probiotics?

    • How to make Whey and at the same time get a fresh cheese that is delightful when mixed with a little onion, salt and pepper and eaten with a potato…it also is called quark in some regions of the world.
      Go to your health store and get a 1/2 gallon or more of organic full milk. Buy a bottle of unflavored organic kefir
      I use Russian kefir…poor all but 1/3rd of the bottle into a clean glass….enjoy.
      Pour the milk into a china bowl or stainless steel container. stir in the rest of the kefir, preheat your oven to its lowest setting (100-150 deg.) insert the covered bowl into the oven on the middle rack. wait 5 min. switch off oven and let the bowl sit in it until the oven cools down. Now you have 2 choices, you may want to let it sit in there for 24 hours or set it on your kitchen counter for 24 hours. I leave mine in the oven. After 24 hours take a clean cheese cloth and line a sterilized strainer with it (I use it double)set the strainer with the cheese cloth onto a second bowl you just had cleaned with boiling water and it has cooled down. Empty your cheese mixture and let it strain inside the fridge for a day or two (depends on how thick and dry you like the cheese)the liquid that collects in the bowl is pure whey and has a multitude of uses.

      • Mark, Since I want to make my own whey (for the fermented ketchup), I’m going to try your recipe for the cheese first. Can you tell me, approximately how much Whey is produced with this recipe? Also, what size bottle of Kefir do you use? Thanks in advance and for the recipe

  3. So I am going to try my 1st fermentation tomorrow (garlic carrots!). I want to try this for my second. My little guy can’t do any sugar, so I’m excited to make my own ketchup with honey, but I have a severe dairy allergy. I’m new to fermentation, but I’ve heard you can leave out the whey, but it just takes a few days longer. Right?

    • You can only leave out the whey when you are fermenting fresh foods that have not been pasteurized. If you will be using canned tomato paste for the ketchup there will be no live organisms in it. Try using some liquid from your fermented carrots (about a tablespoon) instead of whey.

      • That’s good to know as I can’t have dairy and I use canned tomatoes a lot because they are very convenient. I have some liquid from homemade sauerkraut that I can use.

        • I was thinking the sauerkraut as well would be a good choice. I do have fresh SCD 24 hour yogurt / whey that I used to make mine. Lactose and casein FREE. I’ll check it in 3 days.

    • Use whey from lactose free kefir. The fermenting process removes the bacteria that causes the lactose intolerance…just because its called lactose fermentation does not mean lactose intolerant people can’t use it.

      • Usually when people say they have a dairy allergy they mean they are allergic to one of the milk proteins, which don’t go away with fermentation. I am lactose intolerant myself, but that isn’t an “allergy”.

  4. Is there any alternative to whey in this recipe? My daughter is allergic to dairy, so I use extra salt when fermenting vegetables. Any idea if that would work?

    • Use some leftover sauerkraut juice instead or an instant starter culture like this one:

      • Sally Fallon always recommends lemon juice instead of whey. It is enzyme rich and can out-compete bacteria while the lacto builds up.

        • I think the issue with using lemon juice for this recipe is that the tomato paste has been pasteurized, so there is no lactobacili to build up. You need to introduce some form of live culture.

  5. I’m sorry to say a few month ago, I discovered that when anything is “BPA Free”, they substitute something in it’s place. I think it’s BHA but I could be wrong. Unfortunately, whatever it’s called, it’s as bad or worse than BPA. Do a google search for details :-(

    • That’s true but, if the can is BPA free, i believe they line it with nothing.

      • I contacted Native Forest to find out what they used as an alternative to BPA. They gave me a chemical name. Except everywhere I searched for it, it came up as BPA. So, it seems the alternative linings are just as bad as the BPA linings. I don’t see why they can’t just sell everything in glass. I’d pay for the extra shipping costs.

      • Our local natural foods co-op sells a brand (Bionaturae) that comes in glass jars (so the lid probably has BPA, but it is small and isn’t in contact with the tomato paste for very long). They can’t line a can with nothing or the can would get eaten by the acid in the tomatoes (if you leave a can of tomato paste at the back of a cabinet for too long it will start to ooze, even with the BPA-lining). When Muir Glen and other companies were first under heavy pressure to get the BPA out of their can linings, one of their main retorts was that there wasn’t an alternative that had been proven safe. Then they switched, and didn’t say much about their new lining. So I spend the extra for glass, and make sure to freeze what I don’t use in ice cube trays to try to reduce waste and therefore cost that way.

  6. I made this a couple weeks ago and it was really good but then it kept getting mold at the top of the jar. Any ideas on what went wrong?

    • Hmm. I’m not sure. Are you keeping it in the fridge? How long did you let it ferment for? What did you use to ferment it (i.e. whey, sauerkraut juice, etc.)?

  7. For those with true dairy allergies you can still do lactofermentation by making a ginger bug, using 48 hr water kefir or sour, tangy plain kombucha. I use 1/4 cup per quart.

  8. Just curious if during the fermentation process if the sugar is consumed by the cultures similar to water kefir? Or will it still have lots of sugar in it?

    • There is very little sugar added to this recipe. If you are concerned about sugar content, I’d just leave it out. I always use maple syrup and since I use the ketchup in moderation, I don’t worry about this. I’m not sure how much of the sugar gets consumed during the fermentation process. Anyone else care to chime in?

      • Most of the sugar gets eaten up my the culture. That is how and what the culture/bacteria eat, the sugar. When I don’t rinse my milk kefir grains in 2 weeks they smell. I know they are starving because they have eaten up all the milk sugar in the jar. I rinse with fresh milk and store them in fresh milk again in the fridge.

  9. So mine had mold on it too. I made it Friday at 3:00 pm. It had mold Sunday morning. I skimmed it off. Should that be okay? I used whey. Home made 24 (SCD) hour yogurt whey.

  10. How do you know when the ketchup is ready? I made mine Saturday afternoon and today (Monday), I can’t that anything has happened. What exactly are we looking for to indicate it’s done?

    • You may see some bubbles, but with ketchup it’s hard to tell. I’d give it until Tuesday and then stick it in the fridge!

  11. You lost me at bean burger…


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