I came across this information a while ago and I think it is worth sharing.
The Importance of Safe Canning Practices
Utah State University Cooperative Extension Service is here to help you with your canning, food preservation, and food storage questions. There is a USU Extension office located in every county in the state, and a similar extension office in every state in the nation. Our mission is to improve the quality of life for individuals, families and communities through the delivery of practical, research-based information to the citizens of Utah. There are canning practices that we know are UNSAFE. In addition, there are canning recipes and preservation methods that are currently untested, so we cannot say whether or not the items produced are truly safe.
Over the course of the past few months, we have had many questions in our office on the canning and storage of specific products such as cakes and breads, butter, and the long-term storage of whole eggs. There is a lot of information available on the Internet that says that these practices are safe. However, researchers at Utah State University Extension and University of Georgia Extension indicate that these methods do not, in fact, create products that are safe for consumption.
In the end, it is your responsibility to decide how to preserve and store your food. We simply want you to be aware of some of the potential risks involved in the following practices:
1) “Canning” Cakes or Bread in Jars
* The Verdict:
This is a product and method that has been tested by Utah State University Extension in recent years. It will create an unsafe product.
** The Process:
Products such as zucchini bread are baked in wide rimmed canning jars and covered with lids and rings immediately after removing from the oven. As the mixture cools, a vacuum seal is formed.
*** Why This Is Unsafe:
“Canned” breads or cakes, in their final state, are anaerobic (no oxygen), and have both the pH (low-acid) and available moisture in the right range for the growth of C. botulinum. The product has the potential to cause botulism poisoning and kill or seriously impair the person eating the bread.
**** The Research:
Research conducted at USU tried to discover if it was possible to either raise the acid level enough to control the bacteria or add enough sugar to control the water activity and still have palatable zucchini bread. They were unable to create a safe, good-tasting product. For more information, see http://extension.usu.edu/files/publications/factsheet/FN-FS_250_10.pdf
***** More Info:
Botulism growth can begin within 6 to 12 hours at room temperature and the toxin is deadly; the product will likely not show any signs of being contaminated.
2) “Canning” Butter
* The Verdict:
There is currently no research-based safe method for canning butter.
** The Process:
Butter is melted on the stove, then poured into pre-warmed jars, and covered with lids and rings. As the mixture cools, a vacuum seal is formed.
*** What we do know:
Butter is a low-acid product. When we put it in a jar and hermetically seal it (no oxygen), there is a high enough water activity level to allow for the C. botulinum spores to grow and develop the deadly toxin.
**** More Info:
Commercially canned butter can be made because of a high salt-content and special processes not available in a home kitchen. Currently, USU Extension has teamed with BYU’s Long-Term Food Storage Research facility to see if a safe method for canning butter at home can be developed. This is just in the beginning stages, and there is not currently a safe research-based method for canning butter.
3) Storing Eggs on the Shelf
* What we know:
USU Food Scientists have confirmed that Salmonella can survive at room temperature in eggs. Putting oil, Vaseline, or other products on the shell will not protect it from this development.
** The Verdict:
The only way to be sure that an egg is safe for consumption is to keep it at 40°F or slightly lower (the temperature of a refrigerator). If an egg is not stored at this consistent temperature, there is a risk of salmonella growth developing in the egg and contributing to food-borne illnesses.
*** More Info:
Research by Jones and Musgrove (2004) from the USDA Poultry Processing and Meat Quality Research Unit indicate that, when properly handled and refrigerated, eggs are safe for up to 10 weeks (approximately 4 to 5 weeks past the “sell-by” date stamped on the carton). After about 10 weeks, the chemical property of eggs that allow us to, for example, make a fluffy angel cake are changed.
At USU Extension, we are concerned about the safety of Utah County citizens. Our goal is to share research-based information about safe food practices and then allow you to make your own decision regarding your food preservation and food storage practices. If you have questions about whether or not a method of preserving food is safe, please contact an Extension office near you.
Andress, E. L. (n.d.). National Center for Home Food Preservation. Frequently asked canning questions. Retrieved November 13, 2008 from http://www.uga.edu/nchfp/questions/FAQ_canning.html#33<http://www.uga.edu/nchfp/questions/FAQ_canning.html#33http://extension.usu.edu/files/publications/factsheet/FN-FS_250_10.pdf
Brennand, C. P. (2000, October). Safety of canning quick breads. USU Extension Food Safety Fact Sheet, Pub. No. FN-FS-250.10. Utah State University, Logan, Utah. Retrieved November 13, 2008 from
Durham, S. (2004, June 2). Effects of extended storage on eggs. USDA Agricultural Research Service News & Events. Retrieved November 13, 2008 from http://www.ars.usda.gov/is/pr/2004/040602.htm
Musgrove, M. (2004, July). Egg-stending eggs’ usefulness – safely. USDA Food and Nutrition Research Briefs. Retrieved November 13, 2008 from http://www.ars.usda.gov/is/np/fnrb/fnrb0704.htm
Nummer, B. A. (2008, June 12). Hazardous food preparation & storage advice! USU Extension Food Safety Bulletin, No. 009 (2008). Utah State University, Logan, Utah.