NDSU Extension - Richland County


| Share

Food Preservation Facts or Myths?

These Facts and Myths were compiled by Julie Garden-Robinson, PhD, L.R.D., Food and Nutrition Specialist, NDSU Extension Service.

Fact or Myth?

1. Old church cookbooks have great canning recipes you will want to use.


  • Old church cookbooks often provide outdated and UNSAFE canning recipes.
  • Research on food preservation began in the 1940s.
  • USDA canning guidelines underwent a major overhaul in 1994, and in 2006 canning guidelines were reviewed and revised.

2. As long as you boil the jars of vegetables long enough, you will have a safe end product.


  • Unless you can foods properly, you could put yourself at risk for botulism.
  • Clostridium botulinum can grow and produce a toxin in low-acid foods in sealed cans or jars.
  • Boiling jars at 212 degrees will not kill this organism or its spores.

3. Vegetables, meats and most mixtures of foods should ONLY be canned in a pressure canner.


  • The acidity (or pH) of a food determines how foods can be canned.
  • Low-acid foods (pH < 4.6) such as these must be processed in a pressure canner:
    • Vegetables (except when acidified) 
    • Meats 
    • Poultry 
    • Seafood 
    • Soups 
    • Mixtures of acid and low acid foods
  • Yeasts, molds and most bacteria are destroyed at boiling temperatures (212 degrees at sea level) obtained in a water bath canner.
  •  C. botulinum forms spores that require higher temperatures for destruction in a reasonable period of time (usually 240oF or above at sea level).

4. Canning in your oven is a safe, convenient way to seal jars.


  • Canning in an oven is NOT SAFE. 
  • This method can be extremely dangerous for low-acid foods.

5. You can invent your own salsa recipe and can it, as long as you process it in a water bath canner.


  • If you invent your own recipe, you can freeze it.
  • Follow salsa formulations exactly and measure/weigh ingredients carefully.

6. Acid, such as lemon juice or citric acid, should be added to all tomatoes prior to canning.


  • Tomato varieties vary in the amount of acid they contain depending on variety and growing season. 
  • For safety, tomatoes to be canned in a water bath canner OR a pressure canner should be acidified with one of the following:   
    • Add 2 tablespoons bottled lemon juice per quart 
    • Add ½ teaspoon citric acid per quart

7. Most vegetables do not require heat blanching prior to freezing.


  • For best quality, vegetables should be heat-treated (or blanched) in boiling water for the recommended length of time. 
  • Blanching inactivates enzymes (small proteins that regulate processes).
  • Without blanching, undesirable flavor, texture and color changes can occur.

8. You can freeze foods in Cool Whip containers, margarine containers and other clean plastic containers that previously held food.


  • Using these types of containers can result in freezer burn, or dehydration.
  • Freezer burn is a quality issue not a safety issue.
  • You may not want to eat freezer-burned food because of changes in the color, texture and flavor.

9. You can use glass mayonnaise jars to can food, such as peach sauce.

THAT'S A FACT (Kind of)!

  • They are safe to use – BUT Mason-type jars are the best choice for canning.
  • Expect more seal failures and potential breakage when reusing commercial jars.
  • Mayo jars have a narrower sealing surface and are tempered less than Mason jars.
  • Mayo jars may be weakened by repeated contact with metal spoons or knives.
  • Do not use mayonnaise-type jars in a pressure canner because of high risk of jar breakage.

10. Paraffin wax provides an excellent seal on jelly and jam jars.


  • Paraffin wax does not provide an air-tight seal. Spoilage (mold growth) can occur.
  • Use two-piece self-sealing lids on jams and jellies.

11. Pickles are so acidic that they do not need to be processed in a water bath canner.


  • Many molds, yeasts and some bacteria survive in acidic environments.
  • To inactivate molds, yeast and bacteria, process pickles in a water bath canner for the recommended time.

12. Screw bands should be tightened "finger-tip" tight prior to canning.


  • Just use your fingertips – not your “muscles” – to tighten screw bands.”
  • Overtightening can lead to seal failures.
  • Prepare lids as directed on package.
  • Do not reuse lids. You can reuse screwbands
      Creative Commons License
      Feel free to use and share this content, but please do so under the conditions of our Creative Commons license and our Rules for Use. Thanks.