How long depends on the methods you use to can them.

There are 4 different packing methods - Crushed with no added liquid (it is a hot pack method), Whole or Halved Packed in water, whole or halved packed in tomato juice, or whole or halved packed raw with no added liquid.

You can find the processing times for each different method Here

Hot pack and raw pack also require different times and of course the BWB processing time differs from the pressure canning time.

The acidification requirement is 1 T of bottled lemon juice per pint, 2 T per quart. Or you can also use citric acid. Some folks say they can taste the lemon juice, other say they never do. The citric acid gives no taste.

OK?

Dave

Dave thank you for your reply.
Is it necessary to use the lemon juice in all tomato products-such as spaghetti sauce, paste,juice and whole tomatoes? I looked at the site you mentioned and for spaghetti sauce i do not see what pressure to use on the gauge cooker. What about bbb-can't that be used? I have canned for 55 years and didn't realize all this changed.

Is it necessary to use the lemon juice in all tomato products-such as spaghetti sauce, paste,juice and whole tomatoes?

It will vary depending on the other ingredients in the recipe and how it is processed - BWB or PC and the time used for processing.

There are no approved instructions for making tomato paste. It is too thick for proper heat penetration before it would be a scorched taste.

Tomato juice, plain tomatoes, and plain tomato sauce all need the added acid and all can be BWB processed OR PC processed. Times are very different.

Spaghetti sauce has lots of other low acid vegetables in it so it has to be pressure canned only. No lemon juice required. For a gauge canner the time listed there is Table 1 - 11 to 14 lbs. depending on your altitude.

I assume you have also read here about the strong recommendations to convert any gauge canner to weights? The gauges just aren't that accurate and require testing each year for safety. many have been found to be off by as much as 4-5 lbs.

As to all the many changes over the past 55 years (About the same # for me), NCHFP has the info on all of them as well as the recipes. Just let us know if you need to track down some specific info there.

Dave

There are approved instructions for tomato paste but it's in a separate USDA/NCHFP document. I've linked to it below. Due to the density of the paste the processing time for a half-pint jar is 45 minutes and some find the energy cost (as opposed to purchasing tomato paste) excessive.

To add to what Dave said, the standard for acidification of canned tomatoes was introduced in the USDA guide of 1988 after testing begun in 1976 determined that some varieties of tomatoes are low-acid. Growing conditions can also reduce acidity. So this standard has been in effect now for over 25 years.

Lemon juice can be added or citric acid (which I prefer). Vinegar can also be used but will affect the flavor.

Some recipes do not require additional lemon juice. If a recipe like spaghetti sauce does not mention lemon juice or citric acid, you do not need to add it. There are various reasons for this:

1) The recipe has other sources of acid, like red wine.
2) The recipe was tested and developed without the addition of lemon juice and the processing time was changed accordingly.
3) The product has been evaporated through long cooking and the reduced water content has raised acidity. Tomato paste is an example.

I hope this provides additional clarification.

Carol

Here is a link that might be useful: Canning Tomatoes and Tomato Products