Cucumbers are among the most popular foods that are pickled and canned in glass jars.

As the season progresses and gardens begin to overflow with tomatoes, cucumbers and zucchini, home gardeners will be facing the annual question: What am I going to do with all this?

Have no fear. There are plenty of options for storing excess produce. Canning is one of them.

“I think it’s coming back a little bit,” said Jenna Smith, a nutrition and wellness educator with University of Illinois Extension. “It’s one of those things that we see a lot more interest in local foods and sustainable agriculture.”

Canning fruits and vegetables is a relatively simple process, but a little know-how goes a long way. Safety is first, especially with the boiling-water method.

Vegetables with high acid content lend themselves well to canning, though Smith is concerned about some misunderstandings out there. Among them is the belief that tomatoes can be safely canned without any additives.

The villain lurking among some pantries is clostridium botulinum, the bacterium that can cause botulism, a potentially fatal illness.

Canned tomato sauce

“Tomatoes don’t necessarily have as much acid as you might think,” Smith said. “They’re on that borderline. We’ve got thousands of varieties of tomatoes now. They’re all going to have varying levels of pH.”

To be on the safe side, home cooks should add a tablespoon of lemon juice per pint of tomatoes. Citric acid can also be added to increase the acid content.

Evidence of bacterial contamination cannot be determined in most cases.

“Unfortunately there isn’t any way to know,” Smith said. “In home-preserved jars, the lid might become unsealed. But in terms of smell, looks and taste, there is no way of knowing.”

Assorted canned foods

Jams and jellies can generally be canned safely via the boiling-water method because of the presence of sugar and the acid content of the fruits. Pickling cucumbers is also safe due to the addition of high-acid vinegar.

For vegetables such as green beans or corn, a pressure-canning method must be employed. A pressure canner brings the temperature higher than can be achieved in an open pot.

“Pressure canning is going to be needed for those low-acid vegetables and meats,” Smith said. “With the clostridium botulinum that we’re most concerned about, low-acid foods are more likely to have that toxin form. Getting up to that 212 degrees is not going to kill that deadly toxin. That’s why you have to get it up to 240 degrees Fahrenheit.”

There are other methods of preserving fresh bounty from the garden. Among them is dehydration. It is safe and effective.

“It really is popular,” Smith said. “It takes all of that moisture out.”

The worst that can happen is that traces of moisture could be retained in some foods, making them a bit moldy, but not dangerous as with botulism. Smith does point out, however, that jerky requires an extra step.

“A lot of people don’t realize you need another kill step with jerky,” she said. “Either boil the meat in its marinade for five to 10 minutes before you dry it, or after you dry it, stick it in the oven.”

Freezing is another simple form of food preservation. Some vegetables handle it better than others.

“Everyone is going to have their preferences between canned or frozen beans,” Smith said.

“I think canned beans are much better than frozen beans. But I like corn scraped off the cob and frozen.”

The simplest method of all is nothing more than storing vegetables in a cool, dry place; basements usually work fine. Root vegetables such as potatoes, beets and carrots keep for a relatively long time without any other attention.

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Nat Williams is Southern Illinois field editor, writing for Illinois Farmer Today, Iowa Farmer Today and Missouri Farmer Today.