Friday, April 3, 2009

Botulism & Canning Practices

I have recently learned about two canning practices, widely explained on the internet, that are totally unsafe and can lead to serious illness or death via the botulism toxin.

1) The baking of bread or cakes in glass canning jars.

Unsafe practice: A batter of banana bread, zucchini bread or similar cake or bread is spooned into glass canning jars and baked. After baking but while jars are still hot, a canning lid and ring are secured. As the jar cools, the air is removed from the jar and the lid is vacuum-sealed into place.

2) The sealing of butter or margarine in glass canning jars.

Unsafe practice: The butter or margarine is melted and then placed in a glass canning jar. Once again, a canning lid and ring are secured while the jars are hot, and a vacuum-seal is created as the jars cool.
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In both cases, an environment supportive of botulism growth is created. In order for botulism to produce its deadly neurotoxin, it needs three things: no oxygen, low acidity, and a tiny bit of moisture.

If a botulism bacteria is placed in a this environment, it begins to produce a neurotoxin, which if consumed, begins to paralyze muscles. Victims often need antitoxin drugs to deal with it; others need life support when they can no longer breathe on their own, and others succumb and die.

Improper home-canning methods are a major culprit of botulism poisoning.

Canning Rules to Live by:
  • Use a recently published canning book which contains tested recipes. Do not get canning recipes from the internet, old books, word-of-mouth, etc. Do not make up your own recipes.

  • Follow the recipe and instructions exactly. Do not substitute or omit ingredients. This can change the acidity of the product.

  • If the recipe says to pressure cook, do it! Pressure cooking and water bathing are NOT interchangeable methods. A pressure cooker is designed to bring low-acidic food up to higher temperatures.

  • Process according to the appropriate time and pressure.
More Info:


  1. This gives me another reason why I don't can. Thanks Bren!

  2. Jana: Ah stink, that wasn't my intent!

  3. Don't feel bad. I would have never canned anyways. I just want to have reasons why I don't. That is a good one too. I know I would easily be able to grow some botulism. I just feel I would have a knack for it.

  4. i love canning, and do not fear botulism because we take very careful steps with food safety in our kitchen. It saves almost half my food budget, and the simple steps and practices to can safely become second nature after a little while. Don't be discouraged, have a experienced practiced home canner help you if you are afraid of such things. I would also like to mention I do bake banana bread in the jars as mentioned above. While this is not food safe for storage at room temperature, it does package the small cake perfectly to be kept in the refrigerator for two or three days and packed neatly into my family's lunch boxes.

  5. Anonymous: It is unclear from your post if your banana bread (baked in a jar) would be stored in the refrigerator WITH or WITHOUT a sealed lid.

    For the readers of this thread, let me clarify one thing: storing bread in a SEALED jar is DANGEROUS, even if the sealed jar is in the refrigerator. It's the lack of oxygen, low acidity, and moisture within the jar that promotes botulism growth.

    Putting a sealed jar in the refrigerator would not change these conditions and would therefore not eliminate the risk of botulism growth.

    Now, having said that, you CAN bake bread in jars and just NOT seal a lid to the jar. Bread in an UNSEALED jar would be fine in the refrigerator because it would contain oxygen, thus making the food product no different than any other.

  6. At what temperature does botulism spore begin to reoccur?