Yes you do. It can be especially important when recanning previously canned foods (which isn't recommended by the way) because you have no way of knowing for sure if the brand of canned tomatoes added citric acid or not. Some do, some don't.

And the label "marinara" means many different things to different people. It often includes other low-acid ingredients. So without knowing the recipe you used and its ingredients the acidity level is unknown making the added acid - bottled lemon or lime juice or citric acid - even more important.

Dave

Christina - I was just reviewing some marinara recipes and I assume you know that some of them have to be pressured canned? So depending on the recipe you used you may not have to add the lemon juice if it is being pressure canned. Can't say without knowing the specific recipe.

Dave

It was tomatoes I canned, in which I added plenty of citric acid. Also, there weren't many ingredients in the sauce, mainly the tomatoes and onions.

It was tomatoes I canned, in which I added plenty of citric acid. Also, there weren't many ingredients in the sauce, mainly the tomatoes and onions.

And that's the problem. When you say"not many ingredients, mainly the tomatoes and onions" then you are already into unknown territory. Onions are low acid vegetables and in many cases simply adding onions means it requires pressure canning. The standard lemon juice/citric acid recommendations for acidifying plain tomatoes are not enough to also cover onions or garlic, or fresh herbs, etc.

If this is your own recipe rather than one of the approved and tested ones for canning then it is a do-at-your-own-risk activity.

Dave