ACES COVID-19 Response Food Safety
Food Preservation FAQ: Is "dry canning" a Safe Way to Preserve Food?
- "Dry Canning" is method of putting dried food like grains, beans, nuts, into canning jars. Lids are placed on jars then jars placed into an oven and heated to 200F or hotter. In some directions, the food in jars is heated without the lids, which are then placed on the jars when they come out of the oven.*
The short answer is "no".
Here are the issues with this concept:
- This process is not "canning" just because it uses canning jars.
- It's doubtful this process sterilizes the foods, although it might cause vacuum sealing of jars. Or, It's unknown if this process can sterilize the food, although it might cause vacuum sealing of jars.
- This method does not remove all of the oxygen from the jar before sealing and can trap moisture from the food if condensation occurs. Moisture in the jar could support the growth of airborne molds or even bacteria not killed by the low heating in some seemingly dry foods. Some foods may seem dry to the consumer but still have enough moisture in them to come out upon heating and closing up in a container. This could be especially true of home dried foods.
- The dry oven process used at home has never been shown to sterilize these various foods, nor does this extended shelf life. In fact, there is no known researched shelf life for foods packaged just this way at home. Extended shelf life expectations are available for dry foods prepared and packaged by other methods (see the Utah State University Extension references below).
- This heating could even make the quality of some foods worse. This could be either by moisture condensation upon cooling, or if the food is lipid-containing nuts and grains, increased enzymatic reaction causing rancidity.
- A major manufacturer of canning jars and lids in the U.S. does not support the use of their jars and lids/sealing compound in this manner.
- Because this type of process is not recommended, doing it can be a waste of resources, time and energy.
To vacuum seal containers of dry foods, methods that will preserve safely and provide better food quality:
- A vacuum sealing machine that has adapters for jars in addition to sealing bags if you want your food in jars. This vacuum packaging is done at room temperature.
- Oxygen absorbers inside your containers of these foods. Oxygen absorbers can help preserve the quality of foods and also aid in insect control. If you are using the heating method to control for possible insect contamination of your dried food, the Utah State University booklet linked below has methods for heating dry foods BEFORE they are packaged for storage. It also described freezing procedures before packaging as an alternative to insect control.
Here is some advice from Utah State University for long-term storage of dry rice and beans. References for safe methods:
10-year storage of rice: https://extension.usu.edu/foodstorage/howdoi/white_rice
10 or more years for beans: https://extension.usu.edu/foodstorage/howdoi/dry_beans
And here is a large book/booklet from Utah State University about storing food, A Guide to Food Storage for Emergencies: https://extension.usu.edu/foodstorage/ou-files/Food_Storage_Booklet2.pdf
Elizabeth L. Andress, Ph.D.; Professor and Extension Food Safety Specialist
Department of Foods and Nutrition University of Georgia
208 Hoke Smith Annex Athens, GA 30602-4356
web: http://nchfp.uga.edu, https://www.fcs.uga.edu/extension
Nancy Flores, Ph.D.; Extension Food Technology Specialist
New Mexico State University
940 College Dr. Gerald Thomas Hall rm 312 Las Cruces, NM 88003
PH: 575 646 1179; FAX: 575 646 1889