Ask Our Experts

Answers to your questions about gardening, energy, homesteading and other sustainable living topics.

Add to My MSN

Canning Safety Tips

10/8/2010 9:20:09 AM

Tags: canning, safety

I’ve heard conflicting information about the dangers of pressure canning food. How can I be sure the foods I’ve canned are safe to eat? 

Learning to can foods can be intimidating, and it’s certainly important to do it properly. After all, sometimes there are no colors, odors or other handy indicators to betray potentially hazardous canned foods that could make you sick. But canning foods safely isn’t as difficult as you may have heard. 

There are three main things that cause concern: equipment reliability, foodborne illness and altitude adjustments. Let’s get the first one out of the way, because it’s a snap. 

Modern pressure canners are safe. You may have heard about pressure canners of yore exploding when pressurized. Rest assured, the canners available today are much more reliable than they used to be. According to the National Center for Home Food Preservation, home pressure canners were extensively redesigned beginning in the 1970s. Today they all have an automatic vent/ cover lock, a steam vent and a safety fuse. However, it’s still important to carefully follow guidelines that come with your pressure canner, both for safety and to be sure you’re canning at the correct temperature and pressure. (Keep reading.) 

Avoiding foodborne illness is simple. The purpose of canning is to heat the food to a high enough temperature to arrest enzymatic activity and kill yeasts, molds and bacteria. Most of these nasties are knocked out by the acidity of foods or by heat. There are a few pathogens, however — most notably the one that can cause botulism poisoning — that thrive in low-acid foods and can survive temperatures up to 240 degrees Fahrenheit. That’s a potential problem because the temperature of water boiling in an open pan (or in this case, in a water bath-style canner) never reaches much above the boiling point of water — 212 degrees. 

Pressure canners, on the other hand, can reach higher temperatures. Here’s why: These canners trap the steam that escapes from boiling water, thereby increasing the pressure on the liquid. When the pressure is increased, it takes more energy for the liquid molecules to escape the surface, so the temperature at which the water will boil becomes higher. The boiling point in a pressure canner is approximately 250 degrees. 

In short, here is which canning method to use for which foods: 1. Use a water bath canner for acidic foods, such as pickles and many types of fruit. 2. Always use a pressure canner for low-acid foods, such as beans and meat, and for any recipes that combine low-acid with high-acid ingredients, such as salsa and soup. 

Mountain-dwellers: Adjust for your altitude. Cooking at high altitudes can be weird. But the view is well worth it, so I bet you won’t mind making a few adjustments for canning. Here’s the rule: More altitude = more time or more pressure. Instructions on how to adjust for altitude will come with your canner. All of this safety talk should be helpful, but if this is your first introduction to canning, it isn’t enough information to get you started. To learn more, read “Home Canning Basics.Be sure to follow all canning recipes carefully, use clean equipment and always discard any suspicious foods. If in doubt, throw it out! 

—Tabitha Alterman, senior associate editor 

Related Content

The Pantry: Your Home Grocery Store

Preserving the summer harvest by canning and freezing can provide your family with nutritious and fl...

Are Old Canning Recipes Safe to Use?

When it comes to safe methods for canning foods, this is one instance in which modern advice is bett...

The Pressure Canner: My Favorite Preservation Tool

A pressure canner greatly expands the range of foods that can be safely canned at home.

Corporate Social Responsibility and Beekeeping

Beekeeping can bring many benefits other than a great hobby and honey production. Follow Iain as he ...

Content Tools

Post a comment below.


8/17/2011 8:45:40 AM
I'm following a recipe for tomato sauce which specifies removing seeds and skins. Is it safe to leave them in, or do they have a higher pH than the tomatoes themselves and thus raise the pH of the finished sauce?

10/26/2010 6:56:10 PM
Important tip: Vegetables used for canning and pickling must be organically grown. Pesticides inhibit the fermentation process.

Subscribe Today - Pay Now & Save 66% Off the Cover Price

First Name: *
Last Name: *
Address: *
City: *
State/Province: *
Zip/Postal Code:*
(* indicates a required item)
Canadian subs: 1 year, (includes postage & GST). Foreign subs: 1 year, . U.S. funds.
Canadian Subscribers - Click Here
Non US and Canadian Subscribers - Click Here

Lighten the Strain on the Earth and Your Budget

MOTHER EARTH NEWS is the guide to living — as one reader stated — “with little money and abundant happiness.” Every issue is an invaluable guide to leading a more sustainable life, covering ideas from fighting rising energy costs and protecting the environment to avoiding unnecessary spending on processed food. You’ll find tips for slashing heating bills; growing fresh, natural produce at home; and more. MOTHER EARTH NEWS helps you cut costs without sacrificing modern luxuries.

At MOTHER EARTH NEWS, we are dedicated to conserving our planet’s natural resources while helping you conserve your financial resources. That’s why we want you to save money and trees by subscribing through our earth-friendly automatic renewal savings plan. By paying with a credit card, you save an additional $5 and get 6 issues of MOTHER EARTH NEWS for only $12.00 (USA only).

You may also use the Bill Me option and pay $17.00 for 6 issues.