Scientists at Penn State are reminding consumers that recipes for canned breads and cakes are not safe and should not be made at home. Recipes for these items are often appear around holiday time every year. These products are low acid foods with a pH above 4.6, are not shelf-stable, and can’t be safely stored at room temperature. In other words, they can harbor botulism toxin.
These products are made by baking batters in glass canning jars. The jars are removed from the oven and sealed and cooled so a vacuum is created. That’s where the trouble starts; in a vacuum. Clostridium botulism spores grow in unrefrigerated high moisture foods that are low in acid and exposed to little or no oxygen.
Clostridium botulinum bacteria are found everywhere. This bacteria grows under anaerobic conditions found in canning jars. As the bacteria grows, it produces a toxin that is deadly in tiny amounts.
All low acid canned foods must be processed under pressure at temperatures of 240°F or higher. This is the only way to kill the heat-resistant spores the bacteria produces under unfavorable conditions. Research at Penn State found that low acid canned bread or cake products may support the growth of these spores.
If the product is underbaked, that’s another concern. Flour and eggs can harbor pathogenic bacteria such as E. coli and Salmonella. If the product is underbaked, those bacteria can grow as well.
And there’s another hazard with these products: canning jars are not made for use in the oven. They should be used only in hot water baths or pressure canners. When used to bake cakes or breads in the oven’s dry heat, the glass can break and explode.
So don’t use glass canning jars when baking breads and cakes. Use a regular baking pan, cool the product, then use it immediately or freeze it. Or you can give a “mix in the jar” product, which is made by layering the dry ingredients in a jar. The recipient then makes the product using those premeasured dry ingredients, adding the liquid and eggs.
