How to Can Tomatoes at Home — Safely!

Enlarge Image Image Gallery Use these four easy home-canning steps to ensure your tomatoes are both scrumptious and safe. ILLUSTRATION: MOTHER EARTH NEWS STAFF

I canned my first batch of homegrown produce 58 years ago, when I was just nine years old. Countless quart and pint jars later, the tomato remains my favorite garden product to put up ... mostly because it’s my favorite to eat.

I shudder, however, when I think of how many people in this country are innocently using unsafe tomato-canning techniques. For instance, if you are following a canning guide that’s from 1983 or before, you may not be aware that the raw-pack, boiling-water-bath method — commonly used over the past several decades — is no longer considered safe for tomatoes. And I can’t even count the number of times I’ve heard people say — to my horror — that they still can their tomatoes the old-fashioned, open-kettle way because “they never hurt my grandmother or my mother, and they won’t hurt me.”

Granted, botulism poisoning from canned tomatoes is relatively rare — but when you’re talking about a disease that destroys human life, rare isn’t enough. I have seen the ravages of the deadly Clostridium botulinum. It is an insidious killer, for it reveals no clues to its presence: no mold, no odor, no color or taste change. It will grow and thrive in a perfectly sealed (but insufficiently heated) canning jar.

And although tomatoes are generally considered a high-acid food — one that supposedly presents a hostile environment for botulinum — the fact is that their pH can vary greatly, not only by variety, but by a whole range of other factors. Too-green tomatoes, overripe tomatoes, tomatoes from pulled vines, bruised tomatoes, low-acid-type tomatoes, tomatoes grown in low-acid soil ... all have been blamed for producing “killer jars.”

Finally, after years of debate (and the controversy continues), the U.S. Department of Agriculture changed its recommendations for canning tomatoes in 1985: The USDA has dropped the cold-pack, boiling-water-bath method from its list of approved techniques ... recommended that an acidifier be added to tomato products (particularly low-acid and very ripe produce) ... and lengthened its processing-time guidelines for the hot-pack, boiling-water-bath method (more information below).