Fermented Tomatoes are delicious, tangy and a great way to use up and transform homegrown or farmer’s market cherry tomatoes in the summer months. Whether you are a beginner or an expert fermenter, this recipe breaks down everything you need to know from equipment to fermenting safety. All you need are a few simple and fresh ingredients as well as time.
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What is Lacto-Fermentation?
lacto-fermentation or lactic acid fermentation is a preservation method that involves submerging vegetables and/or fruits in a brine solution of salt and water. Rather than killing bacteria (like with vinegar pickling), fermenting takes a different approach.
When done correctly, fermentation kills or suppresses the bad bacteria while allowing the beneficial bacteria to thrive. This fermenting process transforms the vegetables and/or fruits into healthy lacto-fermented food with beneficial probiotics.
If you’ve ever tasted kimchee, Fermented Sambal Oelek (Indonesian chili paste), Fermented jalapenos, fermented cabbage (sauerkraut) or red cabbage sauerkraut, you’ll notice they have an acidity to them that is slightly different from a traditional vinegar pickle. Fermented foods are tangy as opposed to sour/pickled. They may even tingle on your tongue. This fizziness is from the carbon dioxide that is created in the process of fermentation.
I suggest you read my comprehensive post on lacto-fermentation, especially if you are a beginner or this is your first time fermenting. It’ll give you all the basics you need to confidently ferment all the fruits and vegetables! Also, make sure to try my fermented hot sauce recipe and fermented lemons.
Ingredients
This recipe comes together with a few ingredients. Use the freshest tomatoes you can get your hands on. This recipe is perfect to make during the summer months when tomatoes are at their peak.
- Tomatoes: Cherry tomatoes work perfectly in this recipe. You can also use small grape tomatoes or cocktail tomatoes. I wouldn’t use whole tomatoes. You can also use green cherry tomatoes. Check out my pickled cherry tomatoes and pickled green tomatoes recipes too.
- Fresh Herbs: I recommend using woody herbs. Bay leaf and rosemary work nicely, but you can also use oregano and thyme. You could also use fresh basil if you want.
- Salt: When fermenting, use kosher salt, pickling salt, or sea salt. Avoid using table salt as it has added iodine which may affect fermentation.
- Garlic: I love using garlic in all my ferments but the choice is up to you. You can omit the garlic if you prefer.
- Vinegar (optional): At the end of this ferment, I like using neutral white distilled vinegar as it won’t affect the overall flavor, but feel free to use another acid like white wine vinegar, apple cider vinegar, or even lemon juice or lime juice. Avoid using dark vinegar like balsamic or red wine. Adding vinegar is optional, but I recommend it as it helps balance out the flavor and will also help with preserving the peppers for longer in the fridge.
See the recipe card for full information on ingredients and quantities.
Salt and Water Ratio
For this fermented tomatoes recipe, you will be using a salt water brine solution to ferment the cherry tomatoes. This technique can be applied to fermented radishes, fermented carrots, fermented celery, fermented beets, giardiniera mix, and of course fermented cucumbers.
Filtered water or spring water is preferred over tap water because the chlorine in tap water could affect fermentation. I recommend using a 3.5% salt solution. This translates to 3.5 grams of salt per 100 grams of water. A good place to start is 1 tablespoon of sea salt or kosher salt to 2 cups of water (which works out to 17g of salt to 475g of water – a 3.5% ratio).
Equipment and Supplies
Fermentation lids (also known as airlocks or airlock lids) are not essential, but recommended. This is a lid with a special valve that allows gasses to escape safely avoiding any dangerous buildups of gas. The lids fit directly onto a standard mason jar. There are several options like the Klemon and Masontops (affiliate links).
You can use a standard mason jar lid and unscrew it twice a day to let any built-up air escape and quickly reseal. This option is not ideal as it can allow oxygen back in. I recommend using glass fermentation weight (affiliate link) which will keep the peppers submerged in the salt brine. These are also called pickle pebbles.
Use a wide-mouth mason jar because many of the fermenting lids mentioned above are designed specifically for it. This recipe calls for a ¾ quart (approx. 750ml) jar. Glass jars are ideal. I stay clear of metal and plastic containers (though there are many who use plastic containers for fermenting, I choose not to).
Fermenting fruits and vegetables is generally very safe. But to make sure that you are not introducing any bad bacteria or mold in the project and to have a successful ferment, keep your equipment and tools as clean as possible.
You don’t need to sterilize them (as you would if you are water bath canning), but washing everything in soapy warm water and air drying them is the best way to reduce the risk of cross-contamination.
How to Make Lacto Fermented Tomatoes
This is a pretty easy recipe. Read through all the steps before you start. You will have lacto-fermented tomatoes ready to enjoy in about 5 days!
Step 1. Prepare the saltwater brine. In a large measuring cup or jug, combine the water with salt. Mix well to dissolve the salt.
Step 2. Prick the cherry tomatoes. Using a toothpick, poke a few holes in each cherry tomato.
Step 3. Pack the jars. To your mason jar, add the garlic cloves, cherry tomatoes, bay leaf and rosemary sprig.
Step 4. Add the fermenting weight. Add your fermentation weight to the jar, making sure that it does not go above the rim of the mason jar.
Step 5. Pour the brine. Carefully pour the brine solution in the jar, making sure all the tomatoes are submerged.
Step 6. Apply the fermentation lid and ferment. Ferment the cherry tomatoes for at least 5 days away from direct sunlight. On day 5, taste the cherry tomatoes. If you want them to be tangier and sourer, replace the weight and lid and continue to ferment for a few more days. If you’re happy with the taste, remove the weight, and fermentation lid. Add the optional vinegar, apply a regular lid and place the ferment in the fridge.
Fermentation Time, Safety and Storage
While the tomatoes are fermenting keep them on the counter away from direct sunlight. The ideal temperature is room temperature, which is approximately 60°F to 75°F (15°C to 24°C).
Fermentation time will depend entirely on your preference. I recommend a minimum of 5 days. By the 5th day, you’ll notice that the brine may have become a little cloudy. That’s ok.
This is your indication that the lacto fermented cherry tomatoes are ready. Give them a taste. If you like them the way they are, you can proceed to the next step. If you prefer a more tangy flavor, you can do a few more days of fermentation. Tomatoes don’t need to be fermented for a long time like other ferments (homemade sauerkraut for example).
Remember that the finished ferment must be refrigerated! Enjoy within 2 months after refrigeration.
Expert Tips
- Change it up. Feel free to add some other vegetables to your mix like sliced onions and even peppers.
- Clean equipment and clean jars! Wash your jars and utensils well before using them to prevent unwanted bacterial growth using hot soapy water. This is an option but you can sterilize them by boiling them in hot water for 5 minutes. The sterilization isn’t necessary, but does add an extra layer of protection.
- Safety first. Make sure to refrigerate your lacto fermented tomatoes when they are ready.
- Scale up or scale down. You can make this recipe in small batches throughout tomato season. What’s important is to maintain the salt water brine ratio.
Recipe FAQs
A cloudy brine is common with fermentation projects. It’s not really a cause for concern. A cloudy brine will typically form after a few days and is a result of microbial or yeast activity. It can also be from starches and proteins breaking down. Trust your senses. If something smells or looks off to you, it’s best to start over. Read the fermentation safety section in this post.
Yes, you definitely can. This lacto-fermented cherry tomatoes recipe can be used as is with green cherry tomatoes. Follow all the same steps outlined.
Kahm yeast is a type of surface yeast commonly found in fermenting foods such as kombucha, pickles, and sauerkraut. It forms as a thin, white film on the surface of the fermenting liquid and is generally harmless but can alter the flavor and texture of the food.
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Recipe Card
Fermented Tomatoes (How to Ferment Cherry Tomatoes)
Equipment
- Toothpick
- ¾ quart mason jar (24 fl oz mason jar)
- Regular canning jar lid
Ingredients
- 2 cups Fresh unchlorinated water
- 1 tablespoon Kosher salt, sea salt or pickling salt
- 2 Pints Cherry tomatoes - or other small tomatoes
- 1-2 Garlic cloves
- 1 Rosemary sprig
- 1 Bay leaf
After Fermentation is Complete
- 1-2 tablespoon White vinegar - Optional, see note
Instructions
- Prepare the saltwater brine. In a large measuring cup or jug, combine the water with salt. Mix well to dissolve the salt.
- Prick the cherry tomatoes. Using a toothpick, poke a few holes in each cherry tomato. This will help the brine penetrate.
- Pack the jar. To your mason jar, add the garlic cloves, cherry tomatoes, bay leaf and rosemary sprig. Feel free to use smaller/larger jar(s) depending on how many cherry tomatoes you have.
- Add the fermenting weight. Add your fermentation weight to the jar, making sure that it does not go above the rim of the mason jar.
- Pour the brine. Carefully pour the brine solution in the jar, making sure all the tomatoes are submerged.
- Apply the fermentation lid and ferment. Twist on the fermentation lid. Ferment the cherry tomatoes for at least 5 days away from direct sunlight. On day 5, taste the cherry tomatoes. If you want them to be tangier and sourer, replace the weight and lid and continue to ferment for a few more days. If you’re happy with the taste, remove the weight, and fermentation lid. Add the optional vinegar, apply a regular lid and place the ferment in the fridge.
Notes
- Fresh Tomatoes: Cherry tomatoes work perfectly in this recipe. You can also use small grape or cocktail tomatoes. I wouldn’t use larger tomatoes. You can also use green cherry tomatoes.
- Herbs: I recommend using woody herbs. Bay leaf and rosemary work nicely, but you can also use oregano and thyme. You could also use fresh basil if you want.
- Salt: When fermenting, use kosher salt, pickling salt, or sea salt. Avoid using table salt as it has added iodine which may affect fermentation.
- Garlic: I love using garlic in all my ferments but the choice is up to you.
- Vinegar (optional): At the end of this ferment, I like using neutral white distilled vinegar as it won’t affect the overall flavor, but feel free to use another acid like white wine vinegar, apple cider vinegar, or even lemon juice or lime juice.
David Badstubner says
I forgot to prick the tomatoes… should I go back and do that? They’ve only been fermenting for an hour..
Luay Ghafari says
I would strain them out, prick them, and put everything back in the jar. The pricking is key to let the brine penetrate.
Lisa says
Can I add tried coriander leaves?
Luay Ghafari says
You can certainly experiment with herbs as you like.
Francis Quin says
How long do they need to be refrigerated?
Luay Ghafari says
After fermentation is complete and you refrigerate the tomatoes, they should last for around 2-3 months.
Neil Deakin says
When you place in the fridge does this stop the fermentation process so the flavour doesn't get too tangy?
Luay Ghafari says
Essentially yes. Fermentation doesn't stop in the fridge, but it slows down to a crawl so essentially the flavor gets locked in.