You Can CAN Tomatoes! A Guest Post from Erin D.

My dear, wonderful friend Erin wrote up a wonderful step-by-step post on canning tomatoes. I know the season may be too late for many of you, but this post is so brilliant I had to share it. August and September were too hectic to get it up, but I know in other parts of the USA and globe that tomatoes are still available, and for the rest of you I wanted to introduce the canning genius of Erin! Read through it and prepare yourself to can tomatoes next season. Or, get familiar with the process of canning and try preserving something else! Winter is around the corner, after all, and we can extend the bounty of fall ourselves for October Unprocessed! I’m so grateful to Erin for introducing this traditional food preservation method. She’s got great tips for beginners like me. I love her straightforward technique and step-by-step photos. Thank you so much Erin! I think I might throw a canning party soon…

If you are new to home canning, tomato canning is a great way to learn basic preserving techniques. Tomatoes are safe and easy to preserve, and home-canned tomatoes can be used in the place of store-bought canned tomatoes in many recipes. Plus, canning local tomatoes while they are in season allows you to eat local tomatoes all year long.

There is a lot of information about canning online and in cookbooks. My go-to canning guide is a thin paperback book published by Ball, the company that manufactures Ball mason jars. The title is “Blue Book Guide to Preserving “ and you can find it online for under $10. This book has detailed information about canning a range of products and explains the science of preserving.


If you have heard of any home-canning woes, you have probably heard about Botulism. The botulinum toxins that cause Botulism, and other harmful bacteria, can develop in improperly canned foods and cause severe food-born illness. This is a very real concern, so be sure to follow all food safety instructions when canning. The two most important factors in preventing bacterial growth are high acidity and high heat. Acidic produce, such as tomatoes, and added lemon juice creates an inhospitable environment for bacteria. High heat sterilizes jars and eliminates bacteria in full jars. Always pay close attention to details about acidity and heating when canning.


There are a few “must-haves” for a successful canning experience. Ripe tomatoes and lemon juice are required to achieve high enough acidity to ensure a safe product. You definitely need mason jars with two-piece lids (Ball or Kerr brand), and the flat round part of the top must be new. I find that 16-32 oz (pint-quart) jars work best for canning tomatoes. You will need the following kitchen tools: pairing knife, cutting board, large bowl, two large pots, tongs, butter knife, and kitchen towels.

In addition, there are some specialty tools that can make canning much easier. If you plan to can more than a jar or two, I highly recommend buying a “jar lifter” – tongs that have a curved edge to grip jars for easy lifting. You can find jar lifters for under $10 online and at stores that sell canning materials. A second helpful item is a canning pot with a wire rack in the bottom. These pots come in many sizes and range in price, and they make it much easier to process many jars at once. A third item that can be useful at times is a jar funnel to prevent spilling while packing jars. These funnels are cheap and available online or in stores that sell canning supplies.


You could can any type of ripe tomato with the instructions below. I like to use heirloom varieties from local farms because you can’t buy those types of canned tomatoes at the grocery store, they have a range of delicious flavors, and it supports local agriculture. You can also get some great prices on tomatoes from local farms if you buy in bulk (20+ lbs) and get “seconds” tomatoes. “Seconds” are tomatoes that might be slightly over-ripe or bruised – not good enough to slice on a salad, but still good enough to cook. Talk to farmers at your local farmers market about discounts on bulk and “seconds” orders.


Set aside about two hours of your day to can your tomatoes – about 35 minutes of active work, plus 1 hour and 25 minutes for the jars to boil in a water bath.

Step 1: Prepare the Jars

Glass canning jars must be heated and sterilized before they can be filled with produce. There are two very effective ways of doing this: (1) Run the jars through the dishwasher and take them while they are still very hot; (2) Boil the jars for ten minutes in a pot of water. If you are processing many jars of tomatoes and have a dishwasher, then it may be easier to use the first technique. To use the boiling approach, you can place the jar in a pot with a wire rack or kitchen towel under it and fill the pot with enough water to completely submerge the jar. Place the pot on the stove top on high heat and let it reach a boil, then maintain boil for ten minutes. Keep the jars in the hot water until you are ready to fill them with tomatoes. Place the two metal parts of the lid in a bowl of warm soapy water.

Step 2: Prepare the Tomatoes

The tomatoes have to be rinsed, peeled, and cut into pieces that are small enough to fit through the opening in the jars. Cut out the hard stem part and any damaged areas of the tomatoes as well.

{Tomato Peeling Trick: Cut an “X” through the skin on the bottom of the tomatoes and boil them for 1-2 minutes until the skin loosens around the cut. Place the tomatoes in a bowl of ice water – the temperature change further loosens the skins. Take the tomatoes out of the water and the skins should release easily from the meat of the tomato. This process can also be used to peel peaches before canning.}


Step 3: Pack the Jars

Once your tomatoes and jars are prepared, you are ready to start packing. Carefully remove the jars from the hot water (ideally with a jar lifter, or if need be with some combination of tongues and spatulas) and empty out the hot water in the jars. Add LEMON JUICE to each jar: 1 tablespoon if using a pint size jar and 2 tablespoons if using a quart size jar. Fill the jars with tomatoes and pack them down to fit more tomatoes and eliminate air pockets. You can slide a butter knife down the sides of the jar to release bubbles. Leave about ½ inch of headspace at the top of each jar. Then place the two-part tops on each jar and twist to seal them tightly.

Step 4: Process in a Water Bath

Place the filled jars in a large pot on top of a rack or towel. Be sure that the jars are fully submerged in water and bring the water to a boil. Maintain the boil for 1 hour and 25 minutes to properly sterilize and preserve the tomatoes.

Step 5: Pop!

After boiling for the full 1 hour and 25 minutes, carefully remove the jars from the hot water. Place the jars on a metal cooling rack or trivet. When the jars are sufficiently cooled (30-60 minutes), the tops of the jars should “pop”. This “pop” sound is produced when the jar top gets sucked in toward the jar as the air inside the jar compresses while cooling. It indicates that the lid of the jar is completely sealed and the canned tomatoes are safe to store. If the jar’s lid never pops, then you should place the jar in the refrigerator and eat it within a week.

Photo: Properly sealed (“popped”) lid with indent

Step 6: Storage

You may want to rinse the jars before storing them, and you can remove the band part of the lid if you want to. I recommend dating and labeling your jar lid as well. Store your jars away from sunlight in a fairly cool place for best results. Properly canned tomatoes remain good on your shelf for at least one year. After opening a jar, it must be stored in the refrigerator.


You can use your home-canned tomatoes in any recipe that calls for canned tomatoes – like sauces, soups, and stews. I also like to dice my canned tomatoes and add them to pizzas, quiches, and salsas.


Featured Links

Canning 101: The Basic Steps of Canning & Preserving, from Food in Jars

Nine Unofficial Canning Tips from Eating Rules, host of October Unprocessed