Canning 101: Home Canned Tomatoes

The following is a guest post from Marisa of Food in Jars. Welcome, Marisa!

Canned tomatoes are a pantry staple. However for most of us, our tomatoes come in cans from the grocery store. For a moment though, imagine what it would be like to have a pantry lined with sparkling glass jars, filled with home canned tomatoes.

It’s far easier than you might think!

What you’ll need for four quarts of tomatoes:

  • A large stockpot (for processing the jars)
  • A small, round rack (to keep the jars off the bottom of the pot)
  • A smaller pot (for blanching the tomatoes)
  • A tiny saucepan for simmering lids
  • A kettle for boiling water
  • 4 clean quart jars, new lids and rings
  • A paring knife
  • Jarred lemon juice
  • A tablespoon measure
  • 25 Roma tomatoes
  • Boiling water

How to can tomatoes:

1.    Place the rack in the bottom of your stockpot. Make sure to choose a pot that will allow the jars to be submerged with at least one inch of water above them and some room still at the top of the pot to allow for boiling.
2.    Fill the pot with water and begin to bring to a boil.
3.    Fill your smaller blanching pot with water and bring to a boil.
4.    Fill the kettle with water and bring to a boil (yes, there’s lots of water boiling in canning).
5.    Place lids in the smallest pot and bring to a very low simmer.

All photos by Marisa McClellan

6.    While waiting for the blanching water to boil, remove the cores from the tomatoes and carve a small cross into bottoms of the tomatoes, to make them easier to peel post blanching.
7.    Once the smaller pot of water has come a boil, blanch the tomatoes in batches of 3 or 4 (keep the batches small so that you don’t drop the water temperature too drastically) for 1-2 minutes. Use a slotted spoon to remove the tomatoes from the blanching water.
8.    When tomatoes are cool enough to handle, peel them. You should be able to do this with your hands, but keep that paring knife close for the troublesome spots.
9.    Once you have 6 peeled tomatoes, you can fill a jar. If you’re using regular mouthed jars, keep a wooden spoon around, to help you pack the tomatoes into the jars. You should be able to get 5-6 tomatoes into each jar without too much squishing. We’re making whole tomatoes in water here, so do your best not to smash them too much.
10.    Keep peeling and filling jars, until you have four filled jars lined up on your countertop.

11.    Add two tablespoons of lemon juice to each jar.
12.    Top each jar off with the boiling water from the kettle, leaving ½ inch of headspace in each jar.
13.    Using the end of your wooden spoon, remove any air bubbles from inside the jars. Add a bit more water if necessary.
14.    Using a clean kitchen towel or a bit of paper towel, wipe down the rims of the jars.
15.    Place lids on the jars and apply the rings to the jars (don’t tighten those rings too much).
16.    Using jar lifters or tongs (take care when using tongs, it’s easy to give yourself a boiling water burn with them), gently lower the jars into the canning pot. You may need to remove some water, a 2-cup pyrex measuring cup does this task well.
17.    Once all the jars are in the processing pot, put a lid on it and bring it back up to a boil. Adjust the burner temperature to keep the pot boiling gently. Process for 45 minutes.
18.    When the time is up, remove the jars from the pot. Place them on a towel-lined countertop and allow them to cool. The lids should audibly ping as they seal.

Once the jars are completely cool, remove the rings and test the seal by gently tapping the lid. It should hold tight and be concave.

And you’re done! Four quarts of gorgeous, home canned tomatoes are ready for your pantry shelves.

If whole canned tomatoes aren’t really your thing, that doesn’t mean you should rule out home canned tomatoes entirely. Consider salsa, sauce or juice for a start.

Happy canning!

Questions? Pointers? Feel free to discuss in the comments section below.

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154 Comments

  1. How do you core a tomato while keeping it whole? I don’t know how. Some sort of technique with a pairing knife?

  2. Can you use other tomatoes then Roma.. I have Beefy and big boy in my garden right now.. and cherry. I would like can them.

    1. sure, i can cherry tomatoes every year. i add a tablespoon of chopped garlic, hot pack them and process them in a waterbath for the recommended time. awesome!

  3. I’ve been canning for 35+ years and really appreciate your awareness of ‘safe’ canning techniques. I’m thrilled at the revival of interest in canning (and many other homemaking activities) but very concerned about the lack of awareness of using proper timing and cleanliness and understanding acidity, etc. Thank you for being aware of this. I do have a question about this post – when I can whole tomatoes, I always ‘squish’ them in the jars to let the juice out into the jar. I then just need to add a tiny bit of water sometimes to fill it to the proper level but don’t dilute my canned tomatoes by adding extra water. I figure I’m always going to use those tomatoes crushed or chopped up in stews or chunky sauces anyway. What do you use your ‘whole’ tomatoes for that it’s a benefit to keep them whole? I’ve also never heard of coring the tomatoes first – I’ll have to try that the next time I can them.

  4. Kara, when it comes to tomatoes, coring means to just take out that hard nub where it was once attached to the vine. Use a paring knife and cut around the part of the tomato at a 45 degree angle. It’s much the same approach as you’d use when cutting the top of a pumpkin off.

    Julie, you can use other tomatoes. Beefy and big boy both work, although they have more liquid than the meaty roma. Unfortunately, cherry tomatoes don’t can well. They do freeze and dehydrate well, though.

  5. Shenna, the reason I can the tomatoes whole is simply about processing time. When you squish them into the jars and can them mostly in their own juices, best practices call for a processing time of 85 minutes. If you can them whole and pack them in water, you are able to process for just 45. Heat penetrates that water pack more quickly than a pack in their own juices. However, if you want to get into the business of briefly cooking the tomatoes prior to packing them into jars, you can do a “in their own juices” pack and have a shorter processing time. Isn’t it great how many ways there are to can tomatoes!

  6. I have the same question as Julie. I’ve seen the suggestion to use romas before (for salsa, I believe), but I have several different varieties in my garden – does it make a difference in the quality of the canned tomatoes if I use the others?

  7. And I should “refresh” before I ask a question to make sure it hasn’t been answered. Thanks! 😉

  8. Thanks for this post! I’m anticipating a good tomato harvest (my first!) and was hoping this topic would be part of the canning series. Can’t wait to give this a try!

  9. Thanks for these easy-to-understand pointers. I’m still keeping my fingers crossed that my tomato yield will be higher than last summer and I’ll be canning tomatoes for hours!

  10. Why do you specify “jarred” lemon juice? Is there something about fresh lemon juice that makes it unsuitable for canning?

  11. Monica, jarred lemon juice has a dependable acidity level while fresh lemon juice does not. Because you’re adding the lemon juice in order to assure the safety of your tomatoes, it’s best to use that which you know to have the proper acidity. Additionally, when you’re canning 25 pounds of tomatoes, squeezing the number of lemons necessary is a huge task.

  12. I am planning on buying a pressure cooker this year in order to do pressure canning. I’m wondering if I could use this same method, but adjust the processing time?

    I also just bought a european tomato press-thingy. You put in whole tomotoes (skins and all) in the top, turn the crank, and passatto (pureed) tomatoes come out one end and seeds and skins come out the other end.

    I’ve been looking for a canning recipe for passatto tomatoes, but I haven’t been able to find one. I was considering using just a plain tomatoe sauce recipe. But I’m not sure that that would work, and ideally I’d like a recipe that is just plain tomatoes.

    Any ideas?

  13. Faustina, while you can pressure can tomatoes, it’s a slightly different process than the method outlined in this post. I’d recommend getting a copy of a cookbook called “So Easy to Preserve” in order to have detailed instructions for pressure canning process. That book also contains information for canning pureed tomatoes, just like those described in your question.

  14. When I can tomatoes I use citric acid to acidify them rather then lemon juice. I find the taste is not as intrusive on the tomato flavor.

    -Robin

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  16. Robin, citric acid certainly works as well. I’ve just found that it’s easier to get my hands on lemon juice.

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  18. It used to be that the older canning books and recipes did not mention adding citric acid, lemon juice or anything to acidify your tomatoes when canning them. However, with the popularity of Roma and other “meatier” and therefore less watery and less acidic tomatoes the safe practices have changed. Some of the newer recipes will recommend that you can Roma and other “modern hybrids” in, get this, tomato juice as it will acidify things enough. I’m not one for running out and buying tomato juice just for this and, instead, prefer to can the older “heirloom” varieties from my garden. The acidity is noticeably different. I wouldn’t recommend this the first few times but as you get comfortable canning, and, maybe, as you plan a garden this might be remembered if you like to make a lot of chili or tomato sauce come wintertime that you’d plan for a tomato that cans easily and safely in it’s own juices. It’s a personal preference and what you’re looking to use them for in the end. 😀 Wonderful writing and good to see someone give such good instructions. Thank you!

  19. Hi,
    I’ve canned whole tomatoes a couple of times now, I usually do a raw pack, as we like tomato skins, pour boiling water over, add lemon juice and can. Is there a different processing time if I’m leaving skins on and not blanching?
    Also, it seems like I pack them in tight, but by the end of the canning time, all the tomatoes float to the top and I have a third of the jar with just water at the bottom. Do yours do this? Is there a way to pack more in so I don’t have so much “wasted” jar space?
    Thanks!

  20. A raw pack is a raw pack, whether you’re blanching or not, so there’s no different processing time. The only way to get more into the jar is to switch to a hot pack and cook some of the liquid out of the tomatoes before canning.

  21. We spent the whole day canning out bounty of Tomatoes. All our jars have air in top now. My husband thinks we need to throw them out. Can they be salvaged? We are leaving town tomorrow and I can’t use them up cooking right away. They have been sitting out for about 9 hours. Can I put them in the fridge for a week and cook them up when I get back? Or is it too late if they have been sitting out? I would be so grateful for some advice.
    Thanks

  22. Everything I’ve ever canned always has some air in the top… just make sure they were processed at the recommended time and the lids sealed properly and you should be fine.

  23. I just started canning again after about 30 years. My first attempt at tomatoes makes me feel I’ve done something wrong. I filled the jars up with tomatoes and liquid bringing the level to within 1/2 inch of the top. Now that the process is over, there is a good inch of space from the top of the jar down to where the tomatoes start. Is this right, and normal? I forget!

  24. Kathy, that is perfectly normal. Tomatoes sometime lose liquid during processing. As long as the seals are good, the tomatoes should be fine.

  25. I just worked all day and got two quart containers of tomatoes that I canned in Ball containers and boiled in the water but now just saw here that lemon juice is needed – the recipe I had did not mention that so I did not use lemon juice = will my jars be no good? How long will they keep?

  26. Betty, you should put those two jars directly into the refrigerator. Without the additional acid, they’re just not safe.

  27. I’m so excited to find this site!
    I’ve only ever made jam and really want to can some tomatoes. I’ve been trying for years to get my garden to produce enough to put up. If weather holds I might actually get a quart or so out this year and if so I’ll supplement with tomatoes from the farmers market. My daughter is allergic to lemons, limes, pineapples, oranges, etc. how would I substitute the citric acid mentioned for the juice? I know I can get it I’ve seen it in the bulk spice department at my local food co-op. I appreciate any help I could get here. Thank you!

  28. I understand the need for dependable acidity but I am concerned that the jarred lemon juice has preservatives that disagree with family members. What about a teaspoon of vinegar?

  29. Joe, you would need to add four tablespoons per quart of 5% acidity vinegar to sub for the two tablespoons of bottled lemon juice. You can also use 1/2 teaspoon of citric acid instead of lemon juice or vinegar.

  30. I am also wondering if adding acidity is something new as tomatoes are already highly acidic? Did they add this in days of old. I attended a class at williams sonoma where they taught canning tomatoes and beans using a tsp of salt & tsp vinegar per qt , hot packing in dishwasher sterile jars without water bath processing as safe. They emphasized this being done for many generations where nobody ever was sick as a result. I am not condoning this just posing a question.

  31. Joe, I don’t know when it became the norm to add acidity to home canned tomatoes, but it’s been best practices for as long as I’ve been doing it. The methods you describe are highly unsafe, particularly for beans. Modern tomatoes have also been cultivated to be less acidic than their predecessors, so while they once were okay for boiling water bath canning without a great deal of acidification, they aren’t now.

    1. Thanks for staying with this for me and other readers Marisa. Thanks much as I am sure my friends and family will be grateful as well. I also found this at Yahoo I am adding below to further dispel what I was told at Williams Sonoma and certainly supports your advice.

      “Best Answer – Chosen by Voters
      Check out this website for information on canning tomatoes…
      http://www.uga.edu/nchfp/how/can3_tomato…

      I have to disagree with people claiming that tomatoes are acidic enough by themselves. Ripe tomatoes aren’t really that acidic… that’s why the ripe red tomatoes are always prized because they are sweet not acidic/sour.

      The National Center for Home Food Preservation (USA), recommends 2 tablespoons of bottled lemon juice. Acidity of freshly squeezed lemon juice varies depending upon where it was grown and the conditions picked.

      How long they last canned without the juice?
      You really can’t tell… it all depends upon cleanliness and the method you used to can the tomatoes.

  32. Hey Marisa, Can I please ask you about having air in my canned tomatoes? Is this a problem? They look like they are sealed tight. The jars were really full but after water bath processing the tomatoes seem to have shrunk and float to the top of the jar.

    Also I am considering getting a pressure canner. Some reading I have done suggests that this is the only safe method for non acidic canning. Can you shed some light on this as well.

  33. As long as the jars are sealed, the tomatoes should be fine. Floating tomatoes are also normal.

    Pressure canners are the only safe way to preserve low acid foods like vegetables (anything not pickled) and stocks. The UGA website has a lot of good information about pressure canning.

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  35. Hi Marisa, I am looking to buy an All American pressure canner. I have done a lot of internet reading but have confusion based on what various people or sites are saying. First does it take longer to get up to the required pressure with a larger canner? What is the normal processing time expected with a larger pressure canner vs. a smaller one? Thanks again for your advice.

  36. Also, the closest thing to citric acid in my local store was the Ball brand product called Fruit Fresh. This product is Ascorbic acid and citric acid mixed. it contains no sulfites which is good in our home. I know the difference between the two acids but wonder if you have any idea what the percentage of citric acid is in this product? I searched everywhere and came up empty.

  37. I hope you do not mind all these questions. We have been making sun dried tomatoes using your method. We would like to can these so to preserve them longer than a couple weeks and be able to use them to give as gifts. I packed a jar in oil and packed some leafs of parsley in and canned 1 jar. Seems to be ok accept the parsley really darkened up. I could not find any info on canning these tomatoes so what do you think? We buy them sealed in jars so canning them must work no?

  38. Joe, I have only used Presto brand pressure canners, so I can’t advice you on the All American ones. However, I do know people who use and love them. I haven’t heard anything about them taking substantially longer to heat up, although it does make some sense, since they are heavier metal than the Presto ones.

    I also do not know what the percentage of citric acid is in the Fruit Fresh. That product is designed to prevent browning while fruit is processing though. I don’t think it is intended to be used as an acid source. However, I imagine there should be instructions on the jar.

    As far as canning the slow roasted tomatoes, it is not recommended for water bath canning, particularly without additional acidification. However, you could do it in a pressure canner. For more information about canning roasted tomatoes, check out this post: http://dorisandjillycook.com/2009/09/02/canning-roasted-tomatoes/

  39. Hi, We recently (in the last couple weeks) canned roma tomatoes without using any acid, using the recipe from the book “Food Heroes”. This method does not use any added acid or lemon juice. Should we be concerned? Could they possibly be opened, acid added and then re-canned using new seals?

  40. Bruce, tomatoes always need to be acidified when canned. You could uncan them, bring them up to a boil, add acid and recan them. Do make sure to use new lids though, as the original ones will be spent.

  41. I have the same problem as others re canning tomatoes without adding lemon juice in a hot water bath, not using a pressure cooker. Some were canned with adding tomato juice though. To clarify what you said about recanning, can the jars be opened and using the same jarred tomatoes, but with new lids, can the lemon juice simply be added to the previously filled jars, then boiled again for the first recommended time?
    Also, without reprocessing the first set of canned tomatoes, can using them later be safety tested by cracking open the lids to see if the suck in air (safe) or blow out a bit of contents (which would show they are spoiled)? Thanks,

  42. I should also clarify that the tomatoes were canned about 10 days ago, so would they be fine to reprocess?

  43. Morris, typically when you reprocess, you reheat the contents of the jars and then treat the whole process as if it were a fresh, new canning project.

    On the issue of whether your tomatoes are too far gone or now, I honestly can’t say. There’s no set formula here. Chances are good that if you brought everything up to a good, rolling boil and then recanned with lemon juice, everything will be fine. However, there’s no way for me to promise that. It’s a judgment call you have to make.

  44. Thanks for all the good advice, Marisa. I’m allergic to the mold in vinegar, citric acid and jarred lemon juice. Is there anywhere I can find out more details on how to measure acidity or come up with alternatives. Right now I’m freezing my toms but I just ordered 60 lbs and I’m not sure there’s enuf room in the freezer.

    TIA
    Denise

  45. Marisa: This is the best info I’ve seen on the net that really explains the safe way to can tomatoes, with lemon juice and WB or pressure canning processes. Great advice and kudos! The photos are beautiful and instructions easy to understand. I stewed then canned my home grown tomatoes this year, only because the freezer is full with everything else from the garden.

    My question is, is there a safety problem with leaving skin on for crushed/stewed tomatoes, if properly washed and BW bath canned at recommended times?

    I’d like to comment the need to be extremely careful about sanitized surfaces. The 3rd photo shows a roast in the sink next to the canning process. If there were to be some meat juice on the package’s exterior or leaking into the sink, the possibility of cross contamination exists. Best to completely sanitize all canning areas before starting the process to avoid problems.

  46. Hi Marisa. I have been canning away and learning a lot. I ended up buying a presta pressure canner and it works great. I do have one question. Can pressure canning tend to overcook the food you are canning? I have not tried any of the items I have pressure canned yet. It seems like if the food has already been cooked that the additional high temperatures would overcook the item. For instance the clams in clam chowder? Should this be taken into consideration when preparing non acidic foods?

  47. What if there is a little foam at the top of my jarred tomatoes after cooling. They are sealed.

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