It shouldn't matter. Many of my recipes say to add the vinegar or lemon juice at the half way point and continue cooking down until the desired consistency. Sometimes this may take an hour.

Because the tarness doesn't boil out, you may find that they are a bit more sour than you would expect. When I do tomatoes and sauce, I add the citric to the bottom of each jar before its filled.

Prairie-Love

I may have misunderstood what you said about adding the lemon juice and salt. The salt threw me. Lemon juice or vinegar and salt can be cooked down with things like salsa and chili sauce. Were you suppose to put the salt in the jar with the lemon juice before filling? Like Ken said, before filling jars when canning tomatoes.
Otherwise you wouldn't know how many jars you would end up with.
If the recipe said a yield of 7 pints and you ended up with 5, you may have over salted.
Let us know how things worked out.

Well, this is one of those things that has always confused me about this recipe. The instructions are to cook the tomatoes (and onion, garlic, oregano) down to "very thick", then strain through a food mill, THEN add lemon juice and salt to the whole thing. The recipe predicts 7 half-pints. Last year I made this twice and both times I got the expected amount, so was happy that the lemon juice and salt worked out. Yesterday I must have cooked down quite a lot more because I only got 4 1/2 half-pints. I guess I should quit worrying about mistakenly adding the lemon juice and salt too early and worry instead that it will be too salty and too sour :( However, just tasting it, it seemed okay.

These aren't "canned tomatoes", it is a tomato sauce (that I use as a pizza sauce). Why would this be any different than something like chili sauce? As far as cooking the lemon juice down with it, I mean?

It seems like the rules change for every variation and I don't always know why. Why, with sauce or salsa, do you add the acid and salt before, but with just tomatoes you add it when putting in the jar?

Sigh. Maybe one of these days I will know instinctively what's right, but I am sure not there yet!

Thank you!
Ann

The error wasn't so bad if the end product tastes OK. When you can tomatoes you know exactly that you will have 1 quart. When making chili sauce or salsa my recipe calls for maybe 1 tbls. of salt for 20 cups of tomatoes. Not a whole lot of salt for all those tomatoes, but after cooking down until thick, I may end up with 7 pints. That would total slightly less than 1/2 teas. of salt per pint, about what you would use if you were adding salt to a pint of uncooked tomatoes ready to process.
How much salt did the recipe call for?
I keep a canning notebook of all items I process. I write all my formulas down and any changes made.
Also, I put lot numbers on all my canned goods. These lot numbers go into the book also.
Mark in your book, that sauce may be a little salty.