Fermented Tomato Ketchup Recipe

Fermented Tomato Ketchup (Using a Starter Culture)

Ditch the sugar packed ketchup and make your own


You will need:

Many brands of bottled water are unchlorinated, as is filtered water if you use a filter jug. Alternatively, can you try boiling and aerating tap water or leaving tap water to stand for 24 hours.



  1. Mix the tomato paste and maple syrup in a bowl until combined.
  2. Dissolve the Caldwell’s Vegan Starter Culture for Fresh Vegetables in 100ml of unchlorinated water and leave to sit at room temperature for 8-10 minutes to active the starter bacteria.
  3. Mix the culture into the tomato paste until combined.
  4. Add in the salt, allspice and onion powder and mix until all the ingredients are evenly dispersed and the mixture is smooth.
  5. Spoon the ketchup into your glass jars, filling each jar to the shoulder.
  6. Screw on the lids and leave to ferment at room temperature, away from direct sunlight, for 3 days.
  7. After 3 days, stir the ketchup thoroughly then reseal and store in the fridge.

Consume within 3 months


Using fresh tomatoes: 

If you want to add another dimension to your ketchup you can mix in some roughly chopped fresh tomatoes with the rest of your ingredients. This can make your sauce thinner so to avoid this you can dilute your cultures in 50ml of water rather than 100ml.


Why use a fermenting culture?

We like to use the Caldwell’s Vegan Starter Culture for Fresh Vegetables to help stabilise the ferment of our vegetables. The Caldwell’s culture adds essential, good bacteria to the ferment which limits the risk of wild or harmful bacteria developing. Adding good bacteria straight away also helps to speed up the fermentation process.