I’m a member of several groups on Facebook that talk about and apply non-traditional methods of canning. One topic that comes up fairly often is about the current National Center for Home Food Preservation recommendation to add lemon juice to home-canned tomato products. I have personally always added the recommended amount of bottled lemon juice to ensure that my spaghetti sauce and tomato juice have the proper PH level, which should be somewhere in the range of 4.0 to 4.6.
Due to a discussion today, though, I did a little more digging. The first article I came across is this one regarding The Myth of Low Acid Tomatoes. The focus of the article is whether there are low acid tomatoes for people who want or need low acidity in their food: diabetics, those with gastro issues, etc. However, the article includes links to two studies, both done in the 1970’s, about the ph levels of various tomatoes. They tested quite a few varieties and found that ph levels varied from 4.14 to 4.68. Botulism can enter canned tomatoes at 4.8 ph, so it sounds like some tomatoes may be less acidic. But, the article also mentions that riper tomatoes are lower acidity than other tomatoes, and that some of the tomatoes used in the ph testing were orange varieties, which are sweeter, although not necessarily less acidic.
The Centers for Disease Control reported 145 cases of botulism caused by home-canned foods over a period of 18 years (1998-2016). That report does not specify what food caused the botulism cases. However, that same report said that there were 140,000 cases of botulism over that time period, so commercially canned or restaurant prepared foods were probably the causes of the other 139,855 cases of botulism.
My own conclusion is that I will continue to add bottle lemon juice to my home-canned tomato products. We are used to the tiny bit of lemon that we taste in them.
