Sunny Slope Orchard

Sunny Slope Orchard
In the coast range foothills overlooking the Sacramento Valley

Wednesday, September 4, 2013

Tomatoes on My Mind

From our pantry, L-R: Whole canned Juliet tomatoes,
tomato soup, pizza sauce, tomato puree, and tomato salsa
As the summer days grow shorter, it is comforting to gaze at our pantry shelves weighted down with jars of garden produce. For us, tomatoes are a sturdy year-round staple, so we preserve them in several ways. Here are two of our current favorites:

Both of these are tested recipes which can be canned safely at home with a conventional water bath or steam canner. We recommend them highly.

However, for years we have also successfully canned a friend’s delicious tomato soup recipe, even though it hasn’t gotten an official seal of approval from a university or government testing lab. Our research into food safety gave us confidence in this recipe. Here are a few of the resources we found very helpful in our research:

  • The Ball Blue Book was introduced in 1909 and is still a must-have for every home canner, even those of us who grew up canning with our mothers.
  • The National Center for Home Food Preservation is another invaluable resource.
  • In California, contact the University of California Cooperative Extension office to find food preservation classes in your home county. The Extension classes are taught by trained Master Food Preservers.

But, back to our untested recipe: to can or not to can was the question. Traditional wisdom (Mom) always held that botulism cannot grow and form toxin in acid fruit. Tomatoes are an acid fruit. Ergo, there is no botulism toxin in canned tomatoes. However, in recent years many low acid varieties have come onto the market. In addition, non-acid additions like onions or celery reduce acidity of the recipe. Several lessons that we learned helped us decide how to safely can and use our soup recipe.

First, at the recommendation of a Master Food Preserver, we now use a digital meter to test the pH of every batch of tomato soup and all other tomato products before processing. The readings we get are consistently between 4.0 and 4.3 depending on the recipe.  Any tomato product over 4.6 is too low in acidity to be canned safely without the addition of bottled lemon juice, citric acid or vinegar. When measuring pH, we always test the tool with the correct calibration solutions before using it. The soup (or other product) should be tested at room temperature, not when it is too hot or cold. As with any tool, it is important to read the instruction manual and follow the directions.

Digital pH meter for testing acidity
Secondly, the bacteria Clostridium botulinium itself does not harm humans and is in fact widely found in soils. But it produces a toxin under anaerobic, low acid conditions that is potentially fatal. However, according to the Centers for Disease Control  and Prevention, “Despite its extreme potency, botulinium toxin is easily destroyed. Heating to an internal temperature of 85° C [185° F] for at least 5 minutes will decontaminate affected food or drink.”  See

Further, food-borne botulism poisoning is rare in the US. The CDC reports that In the United States, an average of 145 cases are reported each year. Of these, approximately 15% [22 cases] are food borne. And the mortality rate for these cases is 3 to 5% [one death].
See for more detailed data.
Since traffic accidents kill over twenty thousand each year, it would seem that driving to buy your canning lids is actually much more hazardous than eating carefully-preserved home-canned tomatoes.

Finally, a pressure canner raises the internal temperature of the product higher than the boiling point, which will kill botulism spores. So, a good pressure canner might be a wise investment for the serious food preserver.

Sometimes though, the simplest methods are the best. Our fast and easy way to can tomatoes is to run them through our Champion Juicer, a sturdy workhorse from the 1970s. The juice oozes out of the throat of the machine and is captured in a small bowl. We save this juice to freeze for risotto or soup stocks. The pulp is thicker and extrudes through the mouth of the juicer into the larger bowl. Nothing is wasted.

Our trusty Champion Juicer

The pulp is heated to the boiling point, poured into jars and canned either in a pressure canner, boiling water bath or steam canner, following the directions for timing as per the relevant manual. We abandoned the boiling water bath in favor of a steam canner years ago; the water bath kettle full of water was heavy to lift and slow to come to the boil. And the steam canner uses far less water and thus require less energy to heat.
The steam canner is fast and energy efficient

So we encourage everyone to do a bit of research, sharpen your knife, and get in the habit of home canning to bring year round nutrition, economy and above all home grown flavors to your pantry.