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I don't have the stomach for a proper recipe for tomato canning. I simply "binge" bought an enormous box and am now trying to salvage what I can.

Here is my recipe:

  • Gently simmer 6 quarts/litres of tomatoes in a batch on the stove for 24 hours, with a modest one tablespoon of salt as preservative.
  • Wash one-quart/litre mason jars in the dishwasher, along with their covers.
  • Wait until the tomatoes are slightly less than 100C to avoid cracking the jars.
  • Once they're at a still-hot but not boiling temperature (70-80C?), fill the jars.
  • Seal the jars while the tomatoes are still hot.
  • Let cool down, and then put in the fridge.

The tomatoes are still somewhat whole, and so they're versatile. They can be turned into a sauce or used as is in recipes. I could diligently add them right and left to go through them quickly.

Will the tomatoes keep for three months in the fridge?

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The reason that people talk about "proper" trusted recipes in canning is that with anything less than that, all bets are off. Might keep, might not.

That's definitely true of your suggested process: they might keep in the fridge that long, might not, and as a bonus, if you get unlucky, there might be nasty undetectable botulism in there! Tomatoes aren't quite a low enough pH to avoid that, boiling isn't a high enough temperature to kill it either, your process won't even seal the jars, and refrigerator temperatures don't stop it from growing. You're really just using the jars as containers; there's nothing about the process that's actually "canning". You'd get the same results from putting tomato sauce in plastic containers.

And, honestly, a proper recipe is not even much more work than what you're talking about. For example, here's a trustworthy recipe for canned crushed tomatoes, pretty similar to what you want. It's pretty much:

  • blanch and remove skins
  • cut into quarters
  • mash some of them a bit and heat to boiling
  • add the rest
  • add acid (citric acid or bottled lemon juice)
  • put in jars and process (essentially, boil the filled jars for the time specified in the recipe; exhaustive description here)

So basically, that's your process with the addition of acid, and boiling the jars after filling, and it will make them keep at room temperature.

They have a bunch of variations if that's not exactly how you want them prepared.

If you aren't willing to put in that much effort, then I'd really suggest freezing. That removes all of the safety concerns with no complications at all. You can just prepare however you want, put into hopefully smallish containers so you can get at a manageable amount without thawing, and pop in the freezer.

  • Since you don't indicate that blanching and removing the skin is optional, I assume it's necessary (and to also blister one's fingertips while doing it). Is it necessary for aesthetic reasons (so diners do not get tomato skin stuck between their teeth) or for safety reasons (the skin somehow promotes the growth of botulism)? – Calaf Sep 14 '17 at 16:22
  • I don't think skins in canned tomatoes are particularly pleasant, and it's not just that they could get stuck in your teeth. They tend to curl up once they detach from the cooked tomatoes, for a pretty obvious tough, stringy texture. Blending them til smooth is another option, I suppose, if you don't think they're bitter enough to bother you. You can also use a food mill to remove them easily if you want sauce anyway. As far as I know there's no safety issue, it's just that most people don't really like them so all the recipes include how to remove them. I've never searched too hard though. – Cascabel Sep 14 '17 at 16:29
  • From the reuse of the term "process", it appears to have special meaning. I asked for clarification in another comment. – Calaf Sep 14 '17 at 17:24
  • I am not debating that it's much nicer if the skins are removed. I just want the simplest possible recipe, one that will not make me too bitter for having invested a lot of energy if mushrooms appear anyway in the cans when I open them. – Calaf Sep 14 '17 at 17:27
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    Stepping back from that, your goals are fighting with themselves. If you want the simplest possible recipe, and regard this kind of thing as too complex, then you have to give up on the idea of canning altogether, or use an alternative like freezing. If you want something that lasts some length of time, then you need to can properly, i.e. invest a small amount of additional effort beyond your proposed plan, and completely remove the risk. – Cascabel Sep 14 '17 at 18:41
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Three non optional steps when canning tomatoes:

  • use clean jars that you have sterilized and kept hot since in the oven; use new lids that you have heated in hot water to soften the rubber a bit
  • add some salt and acid - lemon juice is good - according to a recipe and depending on jar size
  • process the jars in boiling water (10 minutes for 500 ml / pint; longer for larger jars) an inch or more above the lids

One optional step:

  • blanch them for a minute, drop into ice water, and peel (the skins just aren't very nice in a canned tomato product)

The cooking for 24 hours thing just seems like a whole lot of trouble that doesn't gain you anything in terms of preventing spoilage.

I also sometimes put them through a skins-and-seeds-remover to make sauce, which I simmer for an hour or two to get a stronger flavour. I still add salt and lemon juice jar-by-jar as I fill and process them.

  • I bought "12 decorative mason 1l mason jars". (I didn't choose the decorative part; that's all there was). Does the word "mason" guarantee they will not crack when 1- they will be in the oven (250F?), 2- I pour the tomatoes, 3- process them in boiling water? – Calaf Sep 14 '17 at 17:19
  • From the small sample I tried so far in a recipe, either the 24 hours were helpful, or these (Roma) tomatoes are nice to begin with: The flavor was sublime. It has nothing to do with canned tomatoes. – Calaf Sep 14 '17 at 17:21
  • Is "process" insider lingo for "fill, close, then dip in boiling water"? – Calaf Sep 14 '17 at 17:22
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    Also, you won't crack glass jars from heating them... you'll crack them from shocking them...ie. letting them get pretty cold and then suddenly dropping them into boiling water, or worse, letting them get pretty hot and then dropping them into something cold. Shock will crack them... but normal boiling won't, so don't worry about that. – SnakeDoc Sep 14 '17 at 18:00
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    Processing times are generally longer than that for tomatoes, from what I've seen, e.g. 35 minutes for pints and 45 for quarts in the one linked in my answer. But yes, in any case, it's not just a "dip". – Cascabel Sep 14 '17 at 18:39

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