Elementary Tomato Canning

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.

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.