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Safety of Cakes and Breads in Jars

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Posted: November 30, 2012

Recipes for canning breads and cakes in canning jars appear in newspapers, books, magazines, on television and on the web. While they look attractive and are unique for gift giving, these products are not shelf-stable and cannot be safely stored at room temperature. Canned breads and cakes are typically made by pouring batter into glass canning jars and baking them in the oven. Once the cake or bread is done, the steaming jars are taken out of the oven and then sealed and cooled to create a vacuum. Many recipes claim that they can be stored without refrigeration for about a year. Some say they will keep indefinitely.

The microorganism to be concerned about in these products is Clostridium botulinum. If spores of this type of bacteria are allowed to germinate and grow, deadly botulism toxin is produced. Very small amounts of this toxin can cause an often fatal disease called botulism.  Clostridium botulinum spores are abundant in nature but will only grow and produce toxin in unrefrigerated high moisture foods that are low in acid and exposed to little or no oxygen. These conditions occur in low acid canned foods which must be processed under pressure at temperatures of 240°F or higher to make sure that the heat resistant spores are killed.  Some research studies have shown that low acid canned bread or cake products may have characteristics that are favorable for growth of Clostridium spores.

In addition to the risk of botulism, there is also a significant risk for consumers to become injured from broken glass when baking cakes and breads in glass canning jars. Canning jars are intended for use in hot water baths or pressure canners. They are not designed to withstand the thermal stresses that occur with dry oven heat.

Therefore, Penn State strongly discourages consumers from canning cakes and breads in jars. Botulism is a serious and often fatal disease and no consumer should take unnecessary risks with this microorganism. If someone gives you a home canned cake or bread product, assume that it is unsafe to eat and discard the contents.

Commercially produced breads and cakes in jars or cans are available. This does not mean that the product can be safely duplicated at home. When breads and cakes in jars are made for sale commercially by reputable companies, additives, preservatives and processing controls not available for home recipes are used. Safety tests are conducted for each specific recipe for commercial products. Avoid purchasing canned breads or cakes in glass jars unless they contain additives to prevent microbial growth and meet all labeling requirements for commercial foods.

What are alternatives to canning breads and cakes in jars? Bake the product in a regular baking pan and give it to the recipient who can use it immediately or freeze it.  Most breads and cakes freeze well. A frozen product can be attractively wrapped for gift giving, and the recipient can then choose when he/she wishes to use it. Another alternative is to prepare the ingredients of the cake or bread as a “mix in a jar.” Layer the dry ingredients for a quick bread or cake into a jar and attach the directions for baking it to the outside. Include a “use by” date on the label because ingredients such as baking powder will lose their effectiveness over time; brown sugar will harden when combined with other ingredients, and moisture from nuts and raisins can cause caking of the dry ingredients. Ingredients for a topping, as on a coffee cake, can be inserted into a small plastic bag and placed on top of the other dry ingredients. One month from the time you prepare a “mix in a jar” is an appropriate “use by” date.

Additional information is in the article “Canning Breads and Cakes?” available at the Penn State Food Preservation web site at http://extension.psu.edu/food-safety/food-preservation/faq/canned-breads-and-cakes