There are many varieties of tomatoes available for us to choose from – heirlooms to the newer hybrid varieties. Over the years, the acidity level of tomatoes has been researched, and data collected resulted in the United States Department of Agriculture issuing a statement in 1976 that certain varieties of tomatoes were considered low acid foods and that they must be processed as low acid foods. Since that time, recommendations are to add acid to all tomato products being processed at home.
Because of this research and the resulting recommendations, those of us who have taught home food preservation have encouraged students and all others canning tomato products to add 1/2 tsp of Mrs. Wages® Citric Acid, or 2 Tbsp of bottled lemon juice, or 4 Tbsp of vinegar to each quart of tomato product. This amount of acidification and using the proper processing methods will ensure that your tomato products are safe to eat.
Even though these recommendations have been made since 1976, there are still a number of people who say they have never heard of this. I always heard – “I’ve done this for years and no one ever got sick from eating my food”. My response has always been – it will only take one jar processed improperly to make someone sick or even cause death. I would err on the safe side and add the acid!
There is always controversy about some varieties of tomatoes being more acidic than others. Since there is no economical way to check the acidity of tomatoes for the home canner – be safe and add the acid in the recommended amounts. Heirloom tomatoes, yellow tomatoes, hybrid tomatoes – all should be acidified.
There is one caution regarding the tomatoes you use, however, do not can tomatoes from diseased, dead, or dying vines. This is an indication that the acid level is changing. You may, however, freeze products from these tomatoes. Acidity is also affected by the amount of moisture (rain) the tomatoes have received.
An additional caution is in regards to using produce from flooded gardens. Just remember, if you are in doubt about any food, add it to your compost pile, not to your family’s table.