The Best Ways to Preserve Food, According to UW-Madison Professor Barbara Ingham

A food science expert explains how to safely preserve foods for the pantry.

Photo by Todd Maughan.
Barbara Ingham. Photo by Todd Maughan.

We turned to Barbara Ingham, a professor of food science at UW-Madison, to get the facts on canning, pickling, freezing and drying, some of the most scientific processes one can attempt in a home kitchen. But while great for preserving excess fruits and vegetables, canning and pickling can also make you very, very sick if you don’t know what you’re doing. Knowledge is key.

How do I know if something can be canned?
The first thing is to find where research has provided a recipe that allows you to do it safely. In home canning, people often want to preserve things from the garden or family favorite foods, and that can be very unsafe and potentially deadly.

Canning can be deadly?
The organism we’re most commonly dealing with is Clostridium botulinum [which causes botulism poisoning]. For particular foods, you’ll have to use a pressure canner to destroy it – the spores of this bacteria are naturally present in soil. You’ll see recipes for the canning of meat, green beans or corn that require a pressure canner.

Where can one find these recipes?
I put out information at, under the recipe tab. The other site that’s even more comprehensive is the National Center for Home Food Preservation. Many recipes come from the USDA, and many Wisconsin counties, as we begin to look toward the summer, will start to hold classes.

What makes up an essential starter kit for canning?
If you’re going to be canning low-acid, you’ll need to have a pressure canner. Another thing to consider is size. Your pressure canner needs to hold at least four quart jars, and for boiling water canning, any pot with a rack that’s deep enough to cover the jars in one to two inches of water will work.

What other methods of food preservation exist?
Drying is really fun. I have my dehydrator going a lot in the summer with tomatoes I might use in salads. I also dry tomatoes, mushrooms and spinach, and grind them in a coffee grinder and add the powder to a spaghetti sauce. It’s so flavorful. The other method is freezing.

What’s the biggest mistake people make in freezing vegetables?
Most people don’t like to go through the blanching process, but if you don’t do that, there are enzymes that continue to be active in the freezer, even though it’s very cold. With fruits, they benefit from some kind of sugar pack.

What about pickling?
We make tons of zucchini relish in my family. What are we going to do with all that zucchini if we don’t dry it? There’s also a risk of botulism [with pickling] if the acidity isn’t there.

How can you tell if spoilage has occurred?
If you follow a tested recipe, a properly sealed canning jar will never become unsafe. The only thing that happens over time is that you lose texture, and the vitamins will gradually degrade. A year is ideal, and then after two years, people may notice some changes in color and texture and flavor. Then it might be better compost.

The Epicure’s Guide to Milwaukee

This story is part of The Epicure’s Guide to Milwaukee feature in our March, 2015 issue. Click to read the rest of the guide.

The Epicure's Guide to Milwaukee

‘The Epicure’s Guide to Milwaukee’ is the cover story for the March, 2015, issue of Milwaukee Magazine.
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Matt has written for Milwaukee Magazine since 2006, when he was a lowly intern. Since then, he’s held the posts of assistant news editor and, most recently, senior editor. He’s lived in South Carolina, Tennessee, Connecticut, Iowa, and Indiana but mostly in Wisconsin. He wants to do more fishing but has a hard time finding worms. For the magazine, Matt has written about city government, schools, religion, coffee roasters and Congress.