Why Acidify Tomatoes?

Since tomatoes are naturally acidic, why do we have to acidify them? If you grow an old heirloom tomato that has all of it’s old fashioned acidity and has not been tampered with like some of the newer hybrid low-acid varieties, do you still need to acidify them? Why?

All of my canning books and several places online all agree that tomatoes should be acidified before being canned. It is the pH of the tomatoes that determines whether they are acidic enough alone, or require additional acidity to be safely preserved through the canning process. As I have learned to can more things, I have come across some techniques that I have never heard of before. The question “Why….” tends to come to mind often. This question of acidifying warranted some research on my part to understand why.

To this end, I read through my canning books. Stocking Up and the Ball Complete Book of Home Preserving both recommend always acidifying any tomato product that is canned. The Penn State Extension website explains that the onset of most acidification recommendations came about because of a couple of very unfortunate botulism cases in 1974, which were caused by home canned tomato products. None of us ever want that to occur because of the techniques we used in canning. Jackie Clay’s Growing and Canning Your Own Food also points out the need to add lemon juice to any canned tomato products to insure adequate acidity. Putting Food By points out that “Nowadays home-grown tomatoes often nudge the 4.6 pH cutoff, beyond which they are considered low-acid…”, thus, they would need to be acidified for safe canning.

So, this body of research definitely points to the need to acidify tomatoes. But, back to my original question. If you grow known old-time tomatoes that have been around for 100 years, like the

Arkansas Traveler, do you still need to acidify? There have been many new tomatoes developed with varying levels of acidity. Another thing to consider is the conditions under which the tomatoes are grown and how that may affect acidity. Wiser.org has an interesting article about heirloom seeds. In part, it says, “How are heirlooms defined? A tomato becomes an heirloom after seed savers have grown the same open pollinated (non hybrid) variety over time. A more definitive, but still arbitrary guideline defines an heirloom as being in cultivation for 50 years or more. There are some old commercial varieties that meet the open pollination definition, some of them cross bred from family heirlooms, such as Arkansas Travelers.” Does that mean my Arkansas Traveler tomatoes should be fine for canning without added acidity? It is still a question I have.

While I was pondering and researching I thought I would ask some of my fellow bloggers their opinions on this topic. Here is the question I posed to them and their responses.

Question: “If we grow old heirloom tomatoes, why do we need to acidify them when we can? I have read all of my canning books and some online sources and everyone says that since we can’t determine the acidity of our tomatoes because of the difference in growing conditions, we always need to acidify them. Why? I know there were a few deaths back in the 70′s, and there have been many tomatoes developed for their low acid flavor, but what if we don’t grow those? I guess I feel like some things are just overboard. I thought I would do a post on it and wanted to see if you would contribute your opinion.”
 

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