K-State Research and Extension

Home Canning

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Some things never change.  For instance, whenever the topic of canning arises, you can bet your bottom dollar that a story about someone’s grandmother and her pantry/basement full of jewel-like jars lining dusty shelves is quick to appear on the horizon. 

But, while some things never change, some things DO.  And this definitely applies to the process of home canning foods.  It’s important to remember that food preservation is more science than art, so it’s important to use current (not older than 8-10 years) recipes from a credible source (Extension Office, USDA, National Center for Home Food Preservation, Ball).

Why is this important? Whenever we store food at room temperatures – be it exposed completely to the elements are sealed tightly in a jar – that food is subject to pathogens (microorganisms that cause disease) unless it’s been preserved in a manner that science-based research (not personal/family experience) deems safe for room temperature storage.  This is because pathogens thrive in room temperature environments, so making sure our food is preserved using the most updated research-based methods is imperative for our safety – and the safety of those we feed. 

Here are some updates/FAQs to consider this canning season:

Low/No Sugar Preserves

Making jams and jellies is a great way to preserve extra summer fruits, but most recipes call for many cups of added sugar. While all that sugar certainly impacts the flavor, it also plays a very important safety and functional role. Sugar helps cause the jam or jelly to actually gel and form its distinctive texture. Sugar also binds the water in the product so microorganisms cannot use it to grow; accordingly, sweet spreads that are higher in sugar have a lower risk of spoiling or of making people sick. Therefore, if you are canning a sweet spread, it is essential for safety reasons to use and follow a tested recipe. Do not simply reduce the sugar level on your own. If you are freezing a sweet spread and leave out or reduce the sugar level, the spread may not gel and will be runny. Tested recipes for lowsugar jams and jellies are available from such sources as the National Center for Home Food Preservation; it is very important to use one of these tested recipes if you want to make a safe and high-quality healthier sweet spread.

Avoid Canning White Peaches

Some white fleshed peaches have a natural pH, or acid content, of above 4.6. That makes those peaches a low-acid food. If the recommendations for canning yellow peaches are used for white peaches, they will likely spoil. And it has happened. At this time, there are no recommendations for safely canning white peaches through either pressure or water-bath canning. The best options are to eat them fresh or freeze them.

If It Seals, It’s Safe

Not necessarily.  In some cases, a sealed jar can be the most bio-hazard environment for food.  The bacterium Clostridium botulinum in canned food may cause botulism—a deadly form of food poisoning. These bacteria exist either as spores or as vegetative cells and can survive harmlessly in soil and water for many years.  When ideal conditions exist for growth, the spores produce vegetative cells which multiply rapidly and may produce a deadly toxin within 3 to 4 days of growth in an environment consisting of: a moist, low-acid food;  a temperature; between 40°F and 120°F; and less than 2 percent oxygen.  In other words – a sealed jar of home canned food.

            Last year, an outbreak of botulism claimed the life of one individual and hospitalized 21 others at a church potluck luncheon in Ohio.  The outbreak was linked back to a potato salad that was made with home canned potatoes. 

            Protect yourselves and your loved ones by using updated, scientifically research-based recipes found at your Extension Office, the USDA, the National Center for Home Food Preservation or Ball.  And remember, only use recipes from these sources that have been published within the last 8-10 years.  Those old Ball Blue Books are fun to look at, but they may no longer be safe to use if they’re older than 10 years.

Canning on Smooth Cooktops

            Since the styles of smooth cooktops are manufactured differently, it’s important to refer to your stove’s manufacturer to see if it is suitable for home canning.  Common concerns for canning on smooth cooktops include:

• Damage to the cooktop due to excessive heat that reflects back down on the surface, especially if the canner’s bottom is larger than the diameter of the burner.
• Automatic heat regulators that turn the burner on and off to maintain certain temperatures may not be able to sustain proper heat levels inside canners thus running the risk of under-processing canned foods.
• Some canner bottoms aren’t flat enough to work well on smooth cooktops and may have trouble holding a full boil.

Canning in Pressure Cookers

            The USDA does not recommend using pressure cookers for pressure canning low-acid foods.  Pressure cookers tend to have less metal so won’t conduct heat as efficiently or effectively.  Also, cookers are usually smaller (6 to 8-quarts) and will use less water thus generating less steam which results in under-processed canned foods.

            The USDA recommends using a canner that can hold at least 4 quart-size jars, which is generally a 16-quart or larger canner.

Waterbathing Tomatoes

            Tomatoes can be waterbathed, but you must add two tablespoons of bottled lemon juice or 1/2 teaspoon of citric acid per quart of tomatoes. For pints, use one tablespoon bottled lemon juice or 1/4 teaspoon citric acid. Acid can be added directly to the jars before filling with product. Add sugar to offset acid taste, if desired.  This used to be an unnecessary step in canning tomatoes, but tomatoes available in today’s market are not as acidic as they used to be.

Altitude Adjustments

            Many think Kansas is flatter than a pancake, but a flat pancake can still live at a high altitude.  Kansas altitudes can range from below 1,000 feet to just over 4,000 feet.  Not adjusting for altitude will lead to under-processed food because water boils at lower temperatures in higher altitudes.  If you live over 1,000 feet, then you must adjust your canning recipe to compensate for the higher altitude.  Find your altitude at this website: http://www.veloroutes.org then make the following adjustments:

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