In your opinion is lemon juice a viable addition in order to match the citric acid level in PJ's sauce?
I have never done it, but I understand that some members do use lemon juice as a substitute for citric acid. As an alternative approach, one can use actual citric acid, which is readily available in powdered form. I have a small packet of citric acid that I purchased some time ago from an Indian food store to try to replicate a Pizza Hut pizza sauce, but I couldn't detect a big difference so I did not pursue the matter further.
As you know, Papa John's uses a Stanislaus tomato product, which does include citric acid. By contrast, Escalon, which makes the 6-in-1 products, says that it does not add citric acid to its products, as it notes at http://www.escalon.net/about_us.aspx
where it says:Unlike competitive tomato products, citric acid (a sour tasting preservative) is never added to any Escalon branded product. As a result, the final products are tantalizing in color, and so true to the sweet taste of fresh tomatoes that you will think they were just plucked from the vine.
But, the above quote should not be interpreted to mean that the Escalon tomato products do not have any citric acid. I once spoke with a food broker in the Dallas area who deals with several suppliers of canned tomato products and when I mentioned that Escalon tomato products had no citric acid, he corrected me and said that all tomatoes have some citric acid and that producers of canned tomatoes regularly adjust levels of citric acid in their products. In Escalon's case, it just does not add
any more citric acid to its tomatoes. But it is there naturally and, in that vein, you will often see that a tomato can label says that there is naturally occurring citric acid in their product. It's possible that if the amounts of citric acid are below a certain level the producer/canner does not have to list the citric acid on its labels. I would imagine that there is an FDA regulation on the matter.