Canning Roasted Tomatoes

Roasted tomatoes are delectable little gems. Once you have them, you can use them in sauces, salsa, or just as a topping for bread: Voila! Bruschetta! Freezing is the easiest way to preserve their flavor, but if you have limited freezer space, canning is a good option.

There is, however, a catch. I’ve looked and looked and have been unable to find authoritative canning recommendations for straight roasted tomatoes (no onions). The recipe in the Ball Blue Book is close, with only 1 1/2 c. chopped onions for 12 pounds of Roma tomatoes—but for reasons that aren’t clear to me, this recipe recommends a processing time of 1 hour and 25 minutes. I cannot, for the life of me, figure out why you would need to do this. As you saw in yesterday’s post, the USDA recommends a 40-minute processing time for regular tomatoes. Why would they require twice as long for tomatoes cooked a different way? Is it because their recipe leave the skins on? Does the prolonged heat of roasting do something to the natural acidity of tomatoes? Is it a typo? I’m flummoxed by this. A couple of people at the Clark Park Farmer’s Market this past weekend told me that they treat them like cooked tomatoes (sauce, etc.) and simply process them for 20 minutes in a boiling water bath. Discussion topics on the internets are also inconclusive, with recommendations of everything from not safe, period (this is simply not true), to 20 minutes, to 40 minutes, to 80 minutes.

I can’t tell you why, exactly, but 20 minutes made me nervous. I did, after all, throw in some garlic and herbs and a little bit of oil. I eventually decided to compromise with 10 minutes in the pressure cooker with 15 pounds of pressure. If you don’t have a pressure cooker, I’m not sure what to tell you. If you have all the time in the world and are of the better-safe-than-sorry camp: sure, try 85 minutes. If you’re slightly more adventurous, you might try the regular tomato guidelines: 40 minutes. And if you like to live on the edge or have problems with authority, try 20 minutes…but you do so at your own risk.

Roasted Tomatoes for Canningtomatoes-in-roasting-pan

About 10 pounds tomatoes
4–6 cloves garlic
a few sprigs of rosemary and thyme
A bit of olive oil

1) Cut the tomatoes in half and arrange them face down in a roasting pan. I was able to fit about 5 pounds in a big roasting pan, 2 1/2 pounds in a regular cake pan. Throw in some herbs and garlic and brush a little oil over the tomatoes.

2) Roast at 450°F for about half an hour (more or less depending on the size of the tomatoes) or, better yet, run them under the broiler for 3–5 minutes. However you do it, you’re cooking them until they’re crinkly with a few black spots.

3) Let them cool. Meanwhile, prepare your jars and lids. If you’re using a water bath, bring your water to a boil and sterilize the jars.

4) You can remove the skins, or not, depending on what you want to do with them (Blue Book leaves them on, which perhaps contributes to the longer processing time?). I remove them. Pack the tomatoes in pint jars and run a spatula around the edges to remove air bubbles. Add more if necessary. You’ll find that they shrink quite a bit. My 10 pounds yielded only 3 pint jars. Add some acid if you’re using a water bath: say, 1 T lemon juice, or balsamic vinegar might be nice. Wipe the rims and adjust the lids.

5) Process as best you see fit, as discussed above. Remember, the well-tested but conservative Blue Book says 85 minutes.

Your thoughts?

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30 comments to Canning Roasted Tomatoes

  • katie

    I’ve been freezing roasted tomatoes, but am running out of freezer space so will be giving this a try…will let you know what happens.

  • Zoe

    Looks like the Ball Blue Book is basing its recommendations off of a USDA recipe:

    Im betting that the increased processing time is because roasted tomatoes are essentially considered a ‘raw pack’ because when roasting them, its difficult to really say what temperature they were held at (3 minutes under a broiler is probably not the same as boiling for five minutes) when being cooked.

    What a timely post, I have 10# of maters that I was planning on roasting an canning! Ill be leaving the skins on and processing for 85min in a water bath….

  • Zoe

    Id also make sure that the balsamic is 5% acidity if you are adding it (just in case!) GREAT POST!

  • dorisandjilly

    Good sleuthing, Zoe! But if the USDA does consider it a raw pack, why 85 minutes instead of 40?

  • dorisandjilly

    Oh wow. I see. Those recommendations are even more conservative than those listed on the Web site of the National Center for Home Food Preservation, which says 40 minutes for pints, raw OR hot packed.

    To me, this says that 40 minutes is definitely fairly safe, as the NCHFP is not known for flagrant violation of the rules.

  • Zoe

    Im guessing because it takes longer for raw-packed food to come up to (near) 212 degrees (boiling) than it does for hot packed food (already near boiling when you put it in the jar). Its the temp + time of processing that helps kill any bad micro-organisms and makes the food safe for storage.

    So the 85 minutes is taking into consideration the amount of time needed to bring the food within the jar to temp and *then* the necessary processing time to make the food safe.

    Id also bet that they tack on additional time to cover the cooking of the hot pack food that happens before the food goes in the jar (simmering for 5 minutes).


    Hot Pack:
    Bring food to boil + simmer for 5 minutes + 40 min of processing time


    Raw pack:
    put raw food into heated jar + 85 min of processing time

  • Zoe

    Good Find! Id say given that the NCHFP got that recipe from the USDA I probably have an old version of the recipe and should update! I think that the previous USDA Guide was 1996 or something like that. Up until 6 months or so ago the NCHFP

    Id consider that with the updated info, 40 mins is good to go too!

    (off to update recipe….)

  • localkitchen

    Hi Goats,

    I have a recipe for fire-roasted canned tomatoes at my site, and yes, I go with 40 minutes. After examining the Ball Book, my thinking is that they go with 85 minutes for raw-pack with the worst-case scenario of leaving the toamtoes whole (although the recipe states “whole, halved or quartered) the assumption being that a big honkin piece of tomato will take longer for the heat to fully penetrate. I’ve assumed that with the smaller heirloom tomatoes that I can, and/or with a rough chop (which ends up being more convenient on the using end anyway) 40 minutes is quite safe. After all, they specify 35 minutes for crushed tomatoes (pint) and 45 min (quart). Tomatoes packed in water are also processed for 40 minutes – even if whole – and since mine are chopped, and natural tomato juice has a closer consistency to water than commercial, thick tomato juice, these things all point to the safety of a 40-minute processing time.

    That and the fact that I’m still alive, since that is how I processed all of last year’s tomatoes. 🙂

  • JAR

    The issue is acidity. Acidity is a volatile substance. When you roast tomatoes, you caramelize the sugars, but also roast away the acid. Since acid is a preservative, you need to either add it (recommended for safety), or process longer. I haven’t yet discovered how long one has to do that to be surely safe (I’ll take the 40 minutes a guideline) but I think my stomach has proven its ability to stand up to a lot of stuff.

  • Hi all, I’m new to this canning business and I’m terrified that I’ve done it all wrong.

    If I’m canning raw tomatoes in a pressure cooker, 15 PSI, how long do I process?

    The owners instruction say let it steam for 10 minutes and then pressure cook for 2, and then self cool. I’ve done that and I’m still so dang nervous about using them.

    The water level is a tad below the maters because the float and there’s some air bubbles. Is that normal?

    Also, If I want to can roasted tomatoes, what do you think the method/processing time is safest? (my apologies for being dense if it’s mentioned above)

    Thanks again,


  • dorisandjilly

    Melanie: That should be fine, according to the USDA’s current numbers. At 15 pounds of pressure, they recommend 1 minute for either quarts or pints, hot or cold pack. For 10 pounds of pressure, they recommend 10 minutes. My guidebook from the 70s says 0 minutes is fine. All of these instructions are for 0 to 1,000 feet above sea level.

    In other words: you should be fine! Happy canning!

  • …and those bubbles and lowered water levels? is that normal?

    thanks so much for the information. So helpful and reassuring.

  • by the way, I roasted some of the 200 tomatoes I have in my kitchen today using your instructions as a guideline only i added some balsamic vinegar to the oil, spices and garlic.

    OH MY GOD!!!! i could eat those everyday. I put them in a pasta with homemade pesto sauce.

    Thanks for the fabulous ideas.

  • dorisandjilly

    Melanie: Ideally you’ll have neither bubbles nor lowered water levels, but so long as you have a seal, you’re fine. The bubbles mean that you have some extra air in the jar. Next time be sure to run a spatula around the edges to remove them before putting on the lid. This won’t hurt anything, but it can make it more difficult to achieve a seal. If you lost some water, either a) you didn’t leave enough head space or b) the rings weren’t on tight enough. Again, some loss is normal, and so long as you have a seal, you’re fine.

    So glad you’re enjoying the recipes!


  • Christine Anderson

    I wanted to thank you for your post.

    I roasted some tomatoes, took off the skins and then pureed them and boiled them down into a sauce. I added 1 tbsp of lemon juice into pint jars and processed for 45 minutes in a boiling water canner. It was a hot pack because it was pureed by the time I got done with it.

    I am fully comfortable with the processing time, and I thank you for your evaluation of this.

  • I’m a longtime home canner and own a small commercial cannery. Regarding Jar’s comment, acidity is critical, however, I doubt that’s why USDA has the process time at 85 minutes. I think it’s more of worse case scenario assumption that some folks will stuff large raw tomatoes into jars. If in fact roasting does lower acidity (raise pH), then we should all be cautious. If your end result is at pH 4.6 or above, it won’t matter much how long you process in a hot water bath as botulism toxin will survive that process. For serious home canners like many of you posting here obviously are, I’d strongly recommend investment in pH test strips or a hand held electronic pH meter. My recommendation would be if it’s over pH 4.2 add acid to get it to 4.2, otherwise pressure can it.
    I’m harvesting, roasting and canning this weekend so I’ll test my pH before and after the roasting and let you know my results.

  • Wayne Shoudt

    Looks like I have alot to learn. I fire roast(blacken)and smoke my tomatoes. I also roast vegetables that go in my salsa. The tomatoes go inside(the house) and are crushed a little then simmered on the stove along with the vegetables. I then jar the stuff and waterbath it for about 30mins. I haven’t had any jar failures or made anyone sick. I will invest in PH test strips. any suggestions would be appreciated!

  • Sharon

    Been canning for 20+ yrs + have just started to roast tomatoes to freeze since I found no canning recipes for roasted tomatoes. I’m wondering if I can water bath process the roasted tomatoes in PINT jars instead of QUART jars for the too-long 85minutes. I prefer pint jars mostly for lack of freezer/canning storage space. So, I was wondering if I could substitute the quarts for the pints for 85minutes. Comments?

  • dorisandjilly

    Sharon: It would *definitely* be OK to use pint jars instead of quart jars. In general, you can always go down a size, but not up. Bigger jars generally require a longer time because it takes longer for the contents to heat up.

  • KP

    I am new at canning! My confusion comes from this: I make my own fire roasted salsa… I fire roast the fresh tomatoes, chili’s and garlic cloves. I blacken all of these then blend together all I add is salt for seasoning. I want to can this mixture but am not sure if I have to add an acid??? I really don’t want to change the flavor. What do I do? Should I use a water caner or pressure caner? And for how long do I process this? If anyone can offer advice I would appreciate it.

  • dorisandjilly

    KP: You would need to add some acid to this recipe for make it safe for water-bath canning. I’d recommend something like 1 c. of acid–lime juice, red wine vinegar, cider vinegar, or white vinegar–per 6 pounds of tomatoes. This assumes that the recipe is primarily tomatoes. I’d recommend that you get yourself a copy of the Ball Blue Book and spend some time looking through the various salsa recipes. See which one most closely approximates the proportions used in your recipe, and add a similar amount of vinegar.
    Good luck!

  • I am also new to this and think I am more confused now then when I started- I want to can roasted tomatoes for a Christmas present. If I am cooking for myself I like using the grape tomatoes faced up and slow roast them in an oven with a little S&P, I also love slow roasting whole garlic in olive oil for a long time in the oven. I really want to combine these flavors by roasting both then chopping the garlic and stir it into the tomatoes. The last thing I want to do is make anyone sick.

    Please advise.

    Thank you

  • Denise

    The reason for the longer processing time is because of the olive oil in the recipe. When oil is involved, the processing time is increased as if the item is a low acid food. In fact, I am surprised that it doesn’t require being processed @ 10 pounds of pressure for 90 minutes like is required for qt jars of beans or of raw packed meat. (In fact, that is what I will be doing when I can mine.)

  • plantfreek

    Because even a tiny amount of oil-any oil, can go rancid, your recipe is ripe for growing botulism. That’s why USDA clearly recommends you not use it. No fats are safe in home canning unless you are going to be freezing the product.

  • Sonja

    It is my understanding that roasting reduces the acidity of tomatoes. Therefore, they must be treated as a vegetable, thus, the longer processing time. Not to mention, if the cans are more densely packed, (i.e. 10# per 3 pints), it would take longer for the cans to reach optimal temperature.

  • Lori

    Hahahahaha oops. I thought I was commenting on the cookies recipe I just tried sorry… Thats what I get for having too many tabs open at once on my browser 🙂 Anyway…. I made the roasted tomatoes too yesterday and they were great but time consuming to cut core roast pick off the peels then can.

  • Neerer's Mom

    I only roast my tomatoes. i roast at 400 degrees for 1 hour or more. i cool to touch, peal and bring to a boil and can like any other tomatoes. I did 40 quarts this year without any issues. I dont process just heat up the jars and fill with simmering tomatoes. i have some of the best tomatoes i have ever canned this year.

  • Kris

    In some of my canning recipes talk about citric acid, which will also change the ph, and will not change the flavour of the contents. Also much less is needed than other “adidic” ingredients. Thoughts?

  • Lea

    I contacted one of the companies that produces canning jars. They said they did not advise canning roasted tomatoes on their own as the acidity changes when they are roasted. They saiid to freeze them.

  • GeeGee

    found this on another site…. thought it may help….
    The BWB processing time is directly related to the desity within the jar, the amount of liquid vs. the amount of solids and is not related to the roasting in any way except how it might affect the texture.

    So once roasted, the processing time will depend on how you pack the jars.

    Crushed Tomatoes (with no added liquid) – 35 and 45 min for pints or quarts.

    Whole or Halved Tomatoes (packed in water) – 40 and 45 min

    Whole or Halved Tomatoes (packed in tomato juice) – 85 mins.

    After roasting I’d speculate they would be most like the crushed tomatoes – soft and mushy.

    You can find all the details on each method at NCHFP.


    PS: note that you will have to add the bottled lemon juice or citric acid no matter which processing method you use.