Tomorrow is the first day of September, and with it comes all those traditional end-of-summer events, including tomato canning season (at least here in the mid-Atlantic where I live). Because the yearly tomato glut is finally beginning to arrive, I’ve been getting a number of questions about how to safely can tomatoes.
The most frequent question I get is from people wondering if they can boiling water bath process their favorite spaghetti sauce recipe. You know, the kind that has plenty of garlic, onions, basil, olive oil and sometimes even a few peppers.
Sadly, I always end up delivering disappointing news. You really can’t just can your family recipe. Anything canned in a boiling water bath needs to be high acid (for the science minded types, this means that it has to have a pH of 4.5 or below). This is because botulism cannot grow in high acid environments. However, tomatoes are in the grey zone, typically having a pH right around 4.5. Because of this, tomatoes need to be acidified when canned, so that the acid levels are pushed into the safe zone and the pH becomes something lower than 4.5. That’s why my instructions (and all other good ones you’ll find) for canning whole tomatoes includes two tablespoons of bottled lemon juice per jar (you can also use citric acid if you prefer).
When you make spaghetti sauce, one typically adds a slew of ingredients that, while delicious, lower the acid to seriously unsafe levels. Unless your family spaghetti sauce recipe contains several cups of red wine vinegar, it will be too low in acid to be canned in a boiling water bath.
Most canning information will repeatedly remind you that it’s incredibly important to follow tested recipes. While I will occasionally play around a bit with jams and pickles (and I only do this because I know which aspects can’t be monkeyed with), even I never deviate when it comes to acidifying my tomatoes. I always follow the instructions in either the Ball Blue Book or So Easy to Preserve when I want to preserve tomato sauce, soup and salsas.
The one caveat I have to offer is that if you have a pressure canner, you may be able to preserve your beloved sauce recipe (just so you know, any recipe that includes meat MUST be pressure canned). Pressure canners raise the internal temperature of your jars to temperatures in the neighborhood of 240 degrees, which is high enough to kill off any botulism spores that may exist in your food. However, you should still consult recipes that have been tested using a pressure canner to determine processing time and pressure.
The good news here is that there are plenty of safe, tested tomato recipes that are designed for canning. Let’s hear about your favorites!