How to Can Diced Tomatoes

Avatar David Stillwell  |  Updated: April 30, 2019
How to Can Diced Tomatoes

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Tomatoes are one of the most popular fruits grown in home gardens and with good reason. In my opinion, store-bought tomatoes taste like sawdust, but a perfectly ripe home-grown tomato is fantastic. Even in colder climates, tomatoes can produce a bumper crop if you pick the right varieties. Tomatoes are either determinate or indeterminate. Determinate tomatoes produce all their harvest in a short time, while indeterminate tomatoes spread the yield out across the season. Generally, paste tomatoes are determinate while cherry tomatoes are indeterminate. Because I grow my garden with the intention of canning, freezing or dehydrating food I plant a large variety of both indeterminate and determinate tomatoes. In this article, we discuss how to can diced tomatoes.

How Many Tomatoes Do You Need?

In general, 15 pounds of tomatoes should fill nine-pint canning jars.

If you have a smaller garden, don’t be afraid to mix tomato varieties, if you need more tomatoes to reach 15-pounds. You can also process smaller batches by filling the canner with water-filled canning jars with lids on them. These will keep the jars with tomatoes in them from rolling around during the water bath. Using this method, you can actually can a single pint of tomatoes, though it’s a lot of work for just one pint of tomatoes.

how to can diced tomatoes

How Many Tomato Plants Will You Need?

Each tomato plant is different, and many things impact crop yield. Those factors range from pests to weather and water as well as soil conditions. You will need around 15-pounds of tomatoes to produce nine-pint jars of diced canned tomatoes. Also, there are many other tomato recipes that help to enhance cooking, and that add positively to your short-term food supply. Those include:

  • Pizza Sauce
  • Salsa
  • Red Sauce and Marinara Sauce
  • Ketchup and tomato-based condiments
  • Stewed tomatoes
  • Whole canned tomatoes – Plain
  • Specific sauces – Spiced
  • Hot, Sweet Tomato Jam – fantastic on the grill and on pizza or for cold sandwiches.
  • Etc.

I aim to grow enough tomato plants so that my canning yield is around 500 pounds of fruit. That is roughly 300 – pint jars of diced tomatoes. Ha! I don’t can 300 – pint jars of diced tomatoes. Maybe 75-pints.  The above list is a good representation of what I do with all those tomatoes. I pretty much live on salsa during the fresh-tomato period of the summer. A typical tomato plant in a good growing environment will produce between 15-25 pounds of tomatoes. I plan on 20-pounds per plant and hope for more; Therefore, I plant 35 or so tomato plants each summer. At 20-pounds of fruit per plant, that is about 700-pounds of tomatoes.

That seems like a staggering amount of tomatoes, but it is usually just enough. One-third of the harvest is earmarked for next year’s food supply. This is how I maintain the start of my second year of available food. So, about 100 jars of canned tomatoes – diced or otherwise – are for the following year. The remaining 200 jars are earmarked as food after the tomato harvest ends and the weather turns cold.

How to Can Diced Tomatoes

Diced tomatoes are an easy canning project. They require a water bath canner and a short list of tools and ingredients.  You must add acid to each jar before canning to bring up the acidity level in the tomatoes. More details on this below. You also don’t have to dice them as you can just crush them. They will reduce as they cook. Most people peel the tomatoes, which is an easy process. I don’t. Tomato skins are excellent for gut health as they are roughage and help to clean the gut. To learn more about canning diced tomatoes, just keep reading.

A note about Acidity

Tomatoes vary in acidity by type, and for that reason always add acid to each jar before canning. You can use lemon juice or citric acid.

For Quart Jars use ½ teaspoon of citric acid or if you prefer to use lemon juice then use 2-tablespoons of commercially available bottled lemon juice. I prefer to use citric acid as it comes in a powder that lasts for a while.

For Pint Jars use ¼ teaspoon of citric acid or 1-tablespoon of bottled lemon juice.

canning tomatoes

Getting Started

As a food, we think about tomatoes as being acidic, and they are. However, because different types of tomatoes produce different amounts of acids, we must always add acid to each jar of tomatoes before the canning process. For that reason, you can preserve tomatoes using a water bath canner.

Tools for Canning Diced Tomatoes

The tool list for canning tomatoes is relatively short.  You will need:

  1. A Water Bath Canner
  2. Pint Jars – At least enough to fill the bottom layer of your canner
  3. Lids and Rings for the jar
  4. Jar Tongs – Sometimes called a jar lifter
  5. A canning funnel and a ladle
  6. A bubble tool for removing the bubbles from the packed jar
  7. A couple of clean kitchen towels. I prefer the flour sack towels
  8. A 7-quart stock pot for cooking the tomatoes

Tool List for prepping the Tomatoes

  1. A stock pot – 3-quarts is large enough – you can also use the pot in which you will cook the tomatoes
  2. A large bowel or pot filled with ice water
  3. A slotted ladle or larger slotted spoon
  4. A sharp paring knife.

Prepping the Jars and Lids

The jars, lids, and rings should be washed in warm soapy water and then rinsed. The jars go into a boiling water bath for 15-minutes and then are placed on a towel to air dry – but not totally cool. The lids are also boiled for about five minutes. Diced tomatoes require a hot-pack – the hot fruit is put into warm jars.

Prepping the Tomatoes

  1. Peel them – To peel tomatoes drop ten or so into boiling water until the skins split – 30-45 seconds usually. When the skins split ladle them out of the boiling water and immediately into your bowl of ice water. The sudden cold helps to stop the cooking process. When cool, the outer skin should be easy to remove with your fingers, or you can use a paring knife. TIP: If using a paring knife, all you do is slide the knife under the peel, place your thumb over the tomatoes’ skin where it overlaps the blade and lift up – you are literally peeling the tomato.
  2. Remove bruised areas, stems and the core.
  3. Cut into chunks and place in a large bowl. I generally halve the tomato, remove the blossom and stem remnants, and then cut the tomato into quarters or eighths for larger fruit. I keep the seeds and usually the skins.

The Canning Process

There is very much a dance that happens here, and it requires some patience and timing. It goes like this.

Step 1 – Peel and Core the Tomatoes – I cut mine into quarters and place them in a second bowel. When done, go to step 2.

Step 2 – Fill the water bath canner so that there is at least an inch of water over the top of the jars. Add the clean jars and bring to a boil. As soon as the jars are heating – they will boil for 15 minutes to sterilize them. Begin to cook the tomatoes as outlined in step 3.

Step 3 – Heat the Tomato Quarters —In a large stockpot or saucepan – There are 2 liquid pints to one quart – add 2-4 cups of the peeled tomatoes. Heat over medium heat until they begin to boil. I squeeze the tomato quarters as I add them to the pot. The crushing action help to add liquid to the pot. Once the tomatoes begin to boil, add the rest of the quarters to the pot and heat until the entire batch starts to boil. Reduce the heat and let the pot simmer.  I use a seven-quart, copper bottom pot to heat the tomatoes. I begin this process as soon as the jars are sterilizing in the water bath canner. It can take 15-minutes to cook the tomatoes, and the jars can remain in the boiling water bath longer than 15 minutes.

Step 4 – Heat the Lids and Rings – these will boil for 5-minutes. I put the lids on to heat just after I have added the rest of the tomatoes to the stockpot. TIP: Use a bigger pot then you need to heat the lids because you can use the hot water to top off the water bath canner before you pack the jars.

All these steps should conclude at the same time. You will fill the hot jars with hot tomatoes, add the warmed lid and the jar’s ring. When these steps are ready – the tomatoes have boiled, the jars have sterilized, and the lids are warm, we begin to can.

Step 5 – Remove all the jars from the water bath using the jar tongs. I place the hot jars on a double-folded kitchen towel – mouth-side up. If you need to top up the water bath canner with more water, do so now and bring it back to a boil. TIP: use the hot water from lid pot to top off the water bath canner as that water is already near boiling. TIP: I measure how much water I need in the water bath canner before I start. There must be one inch of water above the top of the jars. By noting this at the beginning of the process, I can make sure there is enough water in there once I add the hot-packed jars. I dislike adding water to the water bath canner once the packed jars are placed.

Step 6 – Add the acid to each jar. – See amounts above.

Step 7 – Hot Pack the jars – leave ½ inch headspace, wipe the rim, place the lid, remove the bubbles, and add the jar’s ring. The ring is NOT tightened. It is only turned until it barely contacts the lid. At this point, the ring’s job is just to hold the lid in place while still allowing air to escape the jar during the water bath. The packed jar goes back into the water bath canner which should still be boiling. Repeat for the remaining sterilized jars.

Step 8 – Once all the hot-packed jars are placed in the water bath canner, turn the heat to high and put the canner’s lid on the top. The jars will process for 35 minutes. Adjust the processing time to accommodate all locations above 1,000 feet in altitude. In general, add five minutes of boiling water canner time for each segment of 3,000 feet in elevation you are above 1,000 feet above sea level. Anywhere under 1,000 feet above sea level process the tomatoes for 35-minutes. I am at 1,100 feet in altitude, and I process the tomatoes for 40 minutes. 1001-3000 feet add five minutes. For 3001-6000 feet at ten minutes (2 altitude segments x 5 minutes each.)

Step 9 – remove the jars from the hot water bath canner and place them on a clean and double folded kitchen towel. These will sit overnight to cool. Do not mess with them while they are cooling as you can cause the jars not to seal. I leave mine for 24-hours at which time I remove the ring and dry it. I then wash the jars off, add a label, replace the ring to the dry jars and store them in my pantry.

High acid foods are good for around 12 months and some for as long as 24-months.

Author’s Bio

David Stillwell is a lifelong naturalist with a background in healthcare and biology who lives in the heart of wildfire territory in Northern California. Prepping for him is a way of life and necessary on a daily basis.  He focuses on food production and agriculture and grows 80% of what he consumes.

Don’t let any vegetable of your harvest go to waste, read the rest of David’s “How to Can” series:

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