Breads and cakes baked in glass jars and then sealed with canning lids are not safe to eat. Ideas for canned breads and cakes in glass jars can be found on the internet and sometimes are printed in magazines, but the bread or cake is not really home-canned. The product is baked in an open glass canning jar and then covered with a canning lid (which seals due to heat); there is no actual ‘canning’ process.
Cake and quick bread recipes contain very little or no acid. Placing these low-acid products in a sealed canning jar may allow for the growth of Clostridium botulinum, and the production of the lethal botulinum toxin. Botulism grows in low-acid canned foods that have been under-processed (products that have not been pressure canned to destroy the harmful organism). Researchers at Kansas State University proved that an organism such as C. botulinum could survive the baking process and multiply in canned quick breads during storage. Using their own banana-nut bread recipe, the researchers at K-State baked the bread in glass jars, and then sealed the jars following methods typically used by consumers. A heat resistant microorganism that is often used in tests to determine when a canning process is adequate, Clostridium sporogenes, was added to the batter for some of the jars. Results showed that the organism, C. sporogenes, survived the baking process and could grow in the product during storage. C. sporogenes is a good indicator of the behavior of C. botulinum. The researchers clearly proved that canned quick breads can be deadly! [Aramouni et al. 1994. Journal of Food Protection. 57:882-886.]
Another idea that should be crossed off your list for holiday gift-giving is pumpkin pie in a jar. This recipe has appeared in newspapers and on web sites over the last week. The idea is that you bake pumpkin pie in a canning jar, top with a decorative crust, and share with family and friends. This creative idea is unsafe because pumpkin pie has to be kept refrigerated. Pies with moist fillings that are low in acid like pumpkin or cream fillings, or even savory meat-filled pies, need to be kept refrigerated in order to remain safe to eat. The fillings for pumpkin, cream-filled, or meat pies present an ideal medium for the growth of harmful bacteria. So, save the health of your friends and family and choose another holiday gift idea. Thanks to Christine Larson (Washington County) who asked about this product.