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Q. I am new at canning! My confusion comes from this: I make my own fire roasted salsa. I fire roast the fresh tomatoes, chiles and garlic cloves. I blacken all of these then blend together. All I add for seasoning is salt. I want to can this mixture, but I’m not sure if I have to add an acid? I really don’t want to change the flavor. What do I do? Should I use a water caner or pressure caner? And for how long do I process this? —KP.
A. Alas, KP, no, this recipe is probably not safe as is. Most fresh salsa recipes are not safe for canning in a boiling-water bath unless you add a significant quantity of acid. The issue with water-bath canning is always whether your final product will have a pH of 4.6 or less (remember, the stronger the acid, the lower the pH). Tomatoes are borderline, and chiles and garlic are definitely low acid. When you can a salsa, you’re basically making a relish: chopped vegetables doused in acid. How much acid you need to add will depend on the exact ratio of tomatoes to chiles to garlic.
My best advice would be to compare your recipe to an approved recipe for regular salsa (you’re unlikely to find one for roasted) and adjust accordingly. The National Center for Home Food Preservation has one that’s 50/50 tomatoes and chiles and uses a total of 1 1/2 vinegar for 6 cups of vegetables. I’ve also developed a recipe for roasted tomato salsa that I believe to be safe for water-bath canning. It’s mostly tomatoes, with a few onions and dried peppers. It includes 1/2 c. lime juice for 8 pounds of tomatoes, which works out to about 1 T. per half-pint, which is twice the normal tomato acidification rule (1 T. lemon juice per pint). I’ve seen similar recommendations for acidifying tomato sauce that includes onions, so this should be enough to keep it safe.
I wouldn’t recommend pressure canning a tomato salsa, even a roasted one. Water-bath processing times vary somewhat, but the most common recommendations call for boiling your salsa for 10 minutes before transferring to the jars, followed by 15 minutes in a boiling water bath.