Myth: Canning your homemade stew, spaghetti and even mashed potatoes is safe.

Answer: BUSTED!

Some people put leftovers from the table in a canning jar and process it long enough to seal the jar. This is not safe. It IS safe to can spaghetti sauce and stew but only from tested recipes. Some foods cannot be canned because it is impossible for the center of the food to reach high enough temperatures to destroy bacteria. Thickened stews and mashed potatoes are examples of foods too thick to can.

Guide sheets for home food preservation can be found at http://extension.missouri.edu/publications. The National Center for Home Food Preservation’s site is http://nchfp.uga.edu.

Contributors: Tammy Roberts (660-679-4167) and Susan Mills-Gray, Nutrition and Health Education Specialists, University of Missouri Extension

Myth: The recipes that I find online for meals in a jar should be safe.

Answer: BUSTED!

Meals in a jar can be convenient and they can make nice gifts, but there is no guarantee that they are safe recipes. There are sites on the internet that suggest you pressure can a chicken soup recipe and then store each jar with a bag of noodles for a quick meal later. That can be done, but the soup is not safe unless it is from a tested recipe. Before spending an entire day preparing meals in a jar, make sure you are using tested recipes for home canning. Don't risk the health and safety of those who will be eating the final product. 

Tested recipes are available through your local Extension office, the National Center for Home Food Preservation and Ball.

• Guide sheets for home food preservation can be found at http://extension.missouri.edu/publications.
• The National Center for Home Food Preservation’s website is http://nchfp.uga.edu.
• The Ball website can be accessed at http://freshpreserving.com.

Contributors: Tammy Roberts (660-679-4167) and Susan Mills-Gray (816-380-8460), Nutrition and Health Education Specialists, University of Missouri Extension

Myth: I can use a microwave for home canning.

Answer: Busted!

As wonderful as microwaves are, they are not appropriate for home canning. The purpose of canning is to destroy bacteria and prevent food-borne illness. Improperly canned foods provide an ideal environment for Clostridium botulinum bacteria to grow. There are only two approved methods for canning food at home — boiling water canning and pressure canning.

Microwaves can’t reach a high enough temperature to safely destroy bacteria. They also heat unevenly, so you can’t guarantee consistent heat to each jar during processing. As a result, cold spots could protect bacteria from being destroyed. There is also a risk of the jars exploding when removing them from the microwave due to the vigorous boil. Use safe canning practices and skip the microwave when canning.

For more information on home canning, see Quality for Keeps: Steps to Success in Home Canning.

Additional nutrition and food safety information can be found at MissouriFamilies.org.

Contributor: Karen Sherbondy, MEd, RD, LD, Extension Associate, Nutrition and Exercise Physiology, University of Missouri Extension, 816-655-6227

Myth: If my jars seal, I know my foods have been successfully canned.

Answer: Busted!

A sealed jar simply means a vacuum has occurred in the jar. Pouring hot food in a jar and quickly applying a lid and jar ring will probably result in a weak seal in that jar. This method is called open kettle canning and is extremely dangerous. Live bacteria easily survive this method of getting a jar to seal. Without adequate processing, live bacteria has become sealed in the jar with the food.

When food is canned at home, two problems must be addressed. First, destroy all dangerous bacteria in the food and in the jar. Second, seal the jar so food does not become recontaminated. Getting a seal only addresses half of the problem.

A sealed jar is of no value if dangerous bacteria survive. Follow these steps to address the issue of destroying all the bad bacteria, yeast and mold that occurs naturally in the environment:

• Wash produce before canning.
• Use up-to-date canning recipes.
• Follow the recommended processing methods and times exactly for each food, jar size and style of pack.
• Use a pressure canner to be safe with non-acid foods like corn, green beans, peas, plain beets and other vegetables.
• Foods that contain natural acidity like fruit or fruit jams and jelly may be safely canned in a water bath canner. Foods that have added acidity like pickles and relishes, may also be canned in a water bath canner.

Now that the food has been prepared and canned properly, you want to ensure a good seal on the jar. A good seal is best produced by water bath canning or pressure canning. Since the jar comes out of the water bath canner at 212 degrees F, it develops a strong seal. Processing a closed, filled jar in a canner kills bacteria that might be in the headspace. The purpose of the seal is to prevent the canned food from being recontaminated by bacteria, yeast or mold.

For more information, visit MissouriFamilies or the National Center for Home Food Preservation.

Contributor: Mary Schroepfer, MS, Nutrition and Health Education Specialist, Franklin County, University of Missouri Extension, SchroepferM@missouri.edu

Not All Foods Can Be Home Canned

Myth: I should be able to safely can any of the canned foods I buy at the grocery store.

Answer: Busted!

Just because you buy something in a jar that was canned, does NOT mean that it is safe for you to try that at home. Commercial canning equipment often hits higher temperatures, operate in sterile environment, include lab testing of representative homogenized batch samples for pathogens, and other safeguards that do not exist in a home kitchen or with home equipment.

Two reliable sources for additional information can be found at Missouri Families or the National Center for Home Food Preservation.

Contributor: Maude Harris, EdD, Nutrition and Health Education Specialist, University of Missouri Extention, harrismau@missouri.edu

Myth: Someone told me I can use any jar for canning, not only the “name-brand” jars.

Answer: Busted!

Mason jars and Ball jars are specifically designed for home canning are best. Commercial mayonnaise jars, baby food and pickle jars should not be used. These jars are generally thin walled in comparison to jars made for home canning and will break more easily. The mouths of the jars may not be appropriate for the sealing lids.

Jars come in a variety of sizes from half-pint jars to half-gallon jars. Pint and quart Ball jars are the most commonly used sizes and are available in regular and wide-mouth tops. If properly used, jars may be reused indefinitely as long as they are kept in good condition.

Two reliable sources for additional information can be found at Missouri Families or the National Center for Home Food Preservation.

Contributor: Maude Harris, EdD, Nutrition and Health Education Specialist, University of Missouri Extention, harrismau@missouri.edu

Myth: I have a hard-water film on my canning jars; so now I have to throw them away.

Answer: Busted!

Before tossing those jars, try to remove the remove scale or hard-water film by soaking the jars for several hours in a solution of 1 cup of vinegar and 1 gallon of water.

In order to reduce scale build-up, try adding ½ cup vinegar to the boiling water bath canner or 2 tablespoons vinegar to the pressure canner before processing.

Two reliable sources for additional information are Missouri Families and the National Center for Home Food Preservation.

Contributor: Maude Harris, EdD, Nutrition and Health Education Specialist, University of Missouri Extention, harrismau@missouri.edu

Myth: I do not have a pressure canner, so it is safe to use my boiling water bath method for all my canning needs.

Answer: Busted!

Pressure canning is the only recommended method for canning meat, poultry, seafood, and vegetables. The bacterium Clostridium botulinum is destroyed in low-acid foods when they are processed at the correct time and pressure in pressure canners. Using boiling water canners for these foods poses a real risk of botulism poisoning.

Low acid foods lack the acidity needed to inhibit the growth of bacteria and spores that can survive boiling water temperatures (212ºF.) A temperature of 240ºF is needed to destroy bacterial spores. This temperature can only be reached in a pressure canner; at 10 pounds pressure or higher.

Two reliable sources for additional information are Missouri Families and the National Center for Home Food Preservation.

Contributor: Maude Harris, EdD, Nutrition and Health Education Specialist, University of Missouri Extention, harrismau@missouri.edu

Myth: If I find mold growing inside a jar of home canned food, I just scrape it off and eat the food.

Answer: Busted!

Mold growth in foods can raise the pH of the food. In home canned products, this could mean that the high acid products could become low acid and therefore run the risk of botulism or other bacterial spoilage. Thus, any home canned product that shows signs of mold growth should be discarded. USDA and microbiologists now recommend against even scooping out the mold on jams and jelly products and using the remaining jam or jelly, even though that used to be suggested.

It is best to follow guidelines set out by So Easy to Preserve, University of Georgia Cooperative Extension Service, and other reliable sources such as Missouri Families or the National Center for Home Food Preservation.

Contributor: Maude Harris, EdD, Nutrition and Health Education Specialist, University of Missouri Extention, harrismau@missouri.edu

Myth: My canned green beans lost some liquid during the processing time; so I can open them to add more liquid.

Answer: Busted!

If the jars were processed correctly and are sealed, DO NOT open them to replace the liquid. If liquid is lost from the jar during processing the food may darken, but it will not spoil. There are several reasons for liquid loss in canning:

• food packed too tightly in jars
• air bubbles not removed before capping the jar
• pressure canner not operated correctly or pressure fluctuating during processing
• lowering pressure in canner suddenly after processing
• opening the canner lid before the pressure has returned to zero
• starchy foods may have absorbed the liquid during canning

It is best to follow guidelines set out by So Easy to Preserve, University of Georgia Cooperative Extension Service, and other reliable sources such as Missouri Families or the National Center for Home Food Preservation.

Contributor: Maude Harris, EdD, Nutrition and Health Education Specialist, University of Missouri Extention, harrismau@missouri.edu

Myth: If the canning recipe calls for cubed pumpkin, the same recipe applies to pureed pumpkin.

Answer: Busted!


It is not safe to home-can pureed pumpkin or any other winter squash (acorn squash, spaghetti squash, butternut squash, etc.). Only cubed squash is safe for home canning.


Canning pureed or mashed pumpkin is unsafe because it is too thick (or viscous) to enable the heat to fully penetrate the product during the canning process. Additionally, research has shown that both viscosity and pH (acidity) are highly variable between batches, making a standard processing time impossible, and unsafe, to determine. Winter squashes are considered low-acid foods (pH >4.6); therefore, if processed incorrectly while canning, these foods have the capacity to support the growth of Clostridium botulinum.


The best option for preserving pureed pumpkin or other squashes is to freeze the product in a freezer bag or plastic container.

Pumpkin butter is a nutrient-rich lower sugar alternative to jam. Make your own:

Ingredients: 1/4 cup water; 1/4 cup packed brown sugar; 2 tablespoons sugar; 3/4 teaspoon each: cinnamon, cloves, nutmeg; 15 ounce can 100% pumpkin puree.

Combine all ingredients except pumpkin in a 1 quart microwaveable bowl. Mix. Microwave on HIGH for 3 minutes. Mix in pumpkin puree and stir well. Microwave on HIGH for 5 minutes.

Keeps in the refrigerator for several weeks.

MYTH: It is safe to use grandma's home canning recipes or canning recipes found on the internet.

Answer: BUSTED!

Home canning is a science that preserves food by killing bacteria, molds, and yeasts; inactivating enzymes; and creating a vacuum in the jar. Recipes should be considered more like the procedure of a science experiment, rather than an old recipe that can be altered as needed. With so many variables at work, recipes are rigorously tested to ensure that, once preserved, foods are safe to store and eat.

An unsafe home-canned food could contain extremely harmful bacteria and toxins if:

• A low-acid food was not processed in a pressure canner at the right pressure for the right amount of time


• The gauge of the canner was inaccurate


• Ingredients were used from a recipe that was not tested for canning


• Proportions of foods in a tested recipe were changed

Only tested recipes from your state's Cooperative Extension Service, USDA, or the Ball Blue Book (dated 1989 or later) are safe to use. Canning procedures from these same sources should be dated 2009 or later to ensure appropriate processing of foods.

Questions about canning? Contact your local MU Extension Nutrition and Health Education Specialist.