Fermented Tomato Conserve (Conserva Cruda Di Pomodoro)

Tomato harvestAs you improve the health and fertility of your soil, you should start seeing some impressive vegetable harvests. This can be a blessing as well as a curse though. Many people know the old but highly accurate joke about the neighbor that leaves a bag of zucchini on the doorstep, rings the doorbell and runs. This is all well and good, but what to do with 100 pounds of fresh plum tomatoes? Or 150 lbs., 200 lbs. or more? The old doorbell trick will only go so far, so let’s look at a delicious alternative! Tomato conserve is a perfect choice.

Drying and canning are always options, very good ones that should be used. There is another ancient method of preserving the bountiful harvest to capture the fresh flavors for the cold winter and gray early spring months when there wasn’t much of anything fresh available. Fermenting fresh vegetables opens up so many flavors and paths to storing this summer’s bounty for the coming winter. We will look at one such method that not only ferments the over-abundance of tomatoes, but concentrates their flavors as a bonus.

A word about fermenting before we begin is in order, so that you don’t come home one day and throw out the entire project due to a misconception or lack of understanding of how the process works. This particular process uses a wild fermentation, meaning the combination of wild airborne yeasts and the naturally occurring bacteria that is on the tomatoes. This wild fermentation is spontaneous; you don’t do anything to help it along. The acid in the tomatoes provide the perfect environment to support lactic acid fermentation. There will be a surface mold which is white and completely normal. Indeed, the white surface mold is needed to protect the tomatoes from rotting. You should not see any colored mold or offensive “rotting” odors.

This process has been used for several hundred years in Italy; probably the first time was shortly after the tomato made its way from America to Italy in the early 1500s. It is still being used today, all across Italy, as small scale home growers put up their harvests to have the flavor of summer to remember during  the coming winter.

The beauty of this method is that it is very scalable, able to handle 20 lbs. in one batch and 100 lbs. or more the next one.

Start with all of the tomatoes washed, stems and any bad spots removed. Get a container that is larger than the amount of tomatoes, so that when all of the tomatoes are crushed there are several inches of space to the top of the container. If necessary, use more than one container. Crush all of the tomatoes and add them to the container. Stir well and cover with a towel, dishcloth or such to keep insects out while allowing air circulation.

The fermentation happens within a few hours and bubbles will appear, with the solids coming to the top and a white mold forming on them. Remember, white mold is good! Stir twice a day, mixing in the mold.

The fermentation will take from 4 to 5 days, depending on temperature and then stop. Remove the solids from the top and strain the mixture through a strainer. One of the best ways to do this is by using a hand cranked device that separates the skins and seeds from the pulp, called a Squeezo or Roma food strainer. The Squeezo is all metal and more expensive but will last several lifetimes!

After straining, keep the pulp and compost the seeds and skins.  (As a side note, it you are wanting to save the seeds from those wonderful tomatoes, just transfer them into another bucket for a second ferment for about a week, scoop off the mold on top and strain out the seeds. Rinse thoroughly and dry on paper towels with the seeds spread out.) The pulp will still have a lot of moisture that needs to be removed. Do this by further straining the pulp in a fine mesh bag or cheese making bag over the sink or a catch bowl. Tie the bag closed, let it hang and drip liquid for a day. It may become covered with a layer of white mold again, just “shave” it off after it finishes the drip process.

The pulp will be noticeably drier and reduced in volume. If the consistency is thick enough for you, stop here. If not, put the bag between two boards or plates with a weight on top to compress it and further drain moisture out for another day or two.

When it is the consistency that you want, traditionally that of firm dough, remove any mold on the bag, open it up and peel it off of the now-firm pulp. The Italians add 25 percent salt to the tomato pulp, but most Americans find this to be way too salty. 10 percent is a good starting point, as it is much easier to add salt than to remove it! Mix the salt in well and let sit. After a few hours knead the mixture just like dough to develop the texture and store it in a jar. It does not need to be refrigerated and will last for several months. In Italy it is usually stored in waxed paper. If you do choose to store it in the refrigerator, it should last for a year.

The end result will be a preserve that is about 8 – 10 percent of the amount of tomatoes you started with. The flavors will be highly concentrated, so a very small amount will add a tremendous amount of flavor to your dishes, from soups, stews and sauces to omelets, dressings and marinades.


13 Responses to Fermented Tomato Conserve (Conserva Cruda Di Pomodoro)

  1. Elaine Westring March 21, 2013 at 6:45 am #

    I had not heard of this way of preserving tomatoes. I will try it this summer. What fun it will be! christmas gift perfect.

    • Stephen March 22, 2013 at 6:50 am #

      There are many traditional foods from around the world that we as Americans don’t know about because of our being educated by the supermarkets on what our foods should look and taste like, or we have lost the cultural connections in the generations since our families immigrated. Cultural or traditional foods are “uncool” to the younger generation, and are often lost after 2 – 3, sadly.

      Enjoy the process, and the concentrated flavor and aroma of summer this coming winter!

      • bob cucarola September 20, 2014 at 12:51 pm #

        ??? You have peaked my interest! Where is the recipe for fermented tomato’s?

      • Stephen September 20, 2014 at 1:34 pm #

        Bob, the “recipe” is in the article! It walks you through how to do the fermentation.

  2. Smitty Smith March 21, 2013 at 7:46 pm #

    I have never heard of this before but it sounds like something I would like to try. Thank You.

    • Stephen March 22, 2013 at 6:37 am #

      Give it a try, Smitty! The flavors are powerful and concentrated, much more so than the tomato paste we are used to.

  3. Jessieann March 22, 2013 at 11:30 pm #

    You are certainly doing your fermentation the hard way. I never have mold. 1 qt. wide mouth canning jar, 1 tables. good quality salt, 1/4 cup whey (liquid from letting raw milk set for 3 or so days to separate whey an curds), green and red cherry tomatoes whole or cut in half, skin seed and all, fill jar tamp down, fill some more cover with pure water and leave a good 1 1/2 inch of head room, screw on lid and let sit at room temp for 3 to 5 days then put in a cool place. The longer is sets in the cool place the more the flavor develops. I have done this with shredded cabbage, beets & turnips, shredded cabbage & celery(yum), carrots (too sweet), winter squash, string beans. The possibilities are limitless. I add herbs and spices too. . Molds have very long fine roots that penetrate deep into food so scraping it off the surface does not get rid of it.
    Great news letter I enjoyed all the articles. I have noticed that the tomatoes and peppers that are deep within the plants, ripen first so they must like some shade.Thanks for the good info. Jessieann

    • Stephen March 25, 2013 at 9:29 am #

      Thanks for the kind words, Jessieann!

      This recipe is meant to concentrate the tomatoes, thus the absence of water during the fermentation process. The white mold that forms is not dangerous and is quite edible, as it is the result of the spontaneous fermentation in the lactic acid environment. The acidity of the tomato fermentation rules out malicious molds! This is how Italians have preserved their excess tomato harvests for several hundreds of years, with the added benefit of reducing the conserve to about 8% of the initial volume of the tomatoes.

      The method you use and describe is the basic vegetable fermentation that I talk about in “Fermented Pepper Sauce” of “Chop, Salt, Pack and Wait. This is great for many vegetables, but is much more work if you want to produce a conserve at the end of the fermentation, as the water dilutes the concentration.

      There are many different methods of fermenting that have been developed and perfected in all parts of the world that we as Americans are simply not used to in today’s world of being educated by the supermarkets as to what our food should look, smell, feel and taste like. Fermentation is just beginning to come back into “style”, as it should!

      • Evelyn D. August 30, 2014 at 2:41 pm #

        Great Article Steven, just what I’ve been looking for to do with all the excess tomatoes this year. Last year? Zero. This year? Well, I have 47 qts. stewed tomatoes, several pints and a few ferments. But, this? Yum, I’m on it right now.

      • Stephen September 4, 2014 at 9:59 am #

        That’s great to hear Evelyn, both about your garden’s production and the amount of food you’ve got put up! Please let us know how you like the fermented tomato conserve.

  4. Paul McCollum September 20, 2014 at 12:32 pm #


    Good article – and useful. I have been fermenting for the past year or so and very much like the results. We have been very dry here in central California (Aromas) but this years tomato and pepper crop have been outstanding. We freeze, make sauces and dry. I will try your recipe and see how it goes.

    I do not know if you remember but I am the one who grew the Sonora wheat that I got from you. Thanks for the great information.

    • Stephen September 20, 2014 at 1:36 pm #

      Good to hear from you, Paul! Yes, please let me know what you think of this fermentation approach.
      And yes, I do remember your photos and information on the Sonoran wheat – I’ve used them in the article about the wheat, as well as in our new seed saving class showing a simple approach to threshing and winnowing dry grains at home.


  1. March 2013 Catalog Highlights | Underwood Gardens - March 21, 2013

    [...] or more? The old doorbell trick will only go so far, so let’s look at a delicious alternative! Fermented Tomato Conserve is a perfect [...]

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