What is Dry Oven Canning?
Dry canning is when jars of prepared foods are placed in a heated oven (usually 200°F or about 93°C) on racks and heated for a minimum of 30 minutes. Once the jars "pop", like in traditional canning, they are considered to be "sealed". The theory is that 200°F temperature is enough to create a sterile environment and that once "processed" these jars can then be stored for years, (many report up to 30 years!) safe from contaminants.
There are a number of concerns with oven canning...
- Oven Thermometers are often inaccurate and it can be very difficult to ascertain when the Contents of the jar has actually reached 200F. There isn't any way to regulate the circulation of heat in the oven. The only way to accurately test the internal temperature of the jar contents would be to remove the lid itself, thereby compromising the food. If you think your oven circulates air evenly think back to the last item you baked in it, was it perfectly browned all over? Did one part of the item brown faster or a bit darker?
- Oven Temperature- the oven cannot be a pressure chamber, which means that the food inside the jars will never get hotter than the boiling point of water (212F) regardless of how high the air temperature is inside the oven, Basic Law of Physics Folks!
- Explosion Risk- Canning jars were not designed to be in a dry heat environment for a prolonged period of time and have been known to crack, shatter and in some instances even Explode during processing.
- Manufacturers of canning jars do not recommend baking or oven canning in the jars.
- Lack of Proof- There isn't a Single, research-based documentation/study to support that 'canning' any food in a dry oven as described on this web page or any page that proposes oven canning provides sufficient heating to destroy bacteria of concern.
- Clostridium Botulinum - aka Botulism THRIVES in an anaerobic environment (like a jar of food!) and is Completely undetectable in an opened jar. It has No Color, No Smell, and causes NO change in taste to alert you to it's deadly presence.
In Short, Oven Canning is a potentially hazardous practice that can lead to food poisoning, botulism and death. There are a number of considerably safer methods of food storage and preservation.
How To Oven Can
If you're not convinced that it's a dangerous practice because you read on the internet that folks have done it and you believe it's safe enough for them, than it's safe enough for you... then here's a How To (btw, we're not responsible for any illness, this is provided for information only).
The ONLY Foods that MAY be "Dry Canned" must contain less than 10% Moisture overall. Those that use this method generally use larger jars such as quart jars, rather than pint jars.
Which food items can be Dry Canned?
- white rice
- whole grains
- dry beans
- powdered milk
- white flour
- pasta without egg (really debatable as pasta contains Oil which can go rancid easily)
- freeze dried foods
- dehydrated foods that are crisp enough to snap such as peas, celery, carrots, onions, yams, sweet potatoes
- cheese powder
- low fat ready-to-eat cereals
Foods that Should NOT be dry canned:
- Pearl Barley
- Nuts - due to the natural oil content
Dry Canning Method (here's how it's recommended on the internet) Clearly you know we DON'T Recommend it at all!
- Wash and dry Jars, be sure the rims are free of cracks and nicks
- Heat oven to 200F
- Fill jars using a canning funnel leaving 1/2" of headspace and place them on a large cookie sheet
- Once all the jars are filled, put them in the oven and "Process" for at least 60 minutes
- Remove the jars from the oven, Wipe the rim of the jar, place a lid on and screw the band down tight
- When the lids "Ping" they are said to be sealed.
- Cool in a draft free spot
- Label and date the jars and store in a cool dark place
What this method does for Dry Goods:
- Kills eggs, larvae of bugs, preventing them from hatching
- Reduces moisture in already low moisture foods to help prevent staleness
What this method does Not Do:
- Kill Bacteria Spores
- Kill Mold Spores
- Jar Frogging- foods that contain more than 10% moisture will "frog-up" and cause mold to grow.
- National Center for Home Food Preservation ~Link~ Advises NOT to can with this method
- USDA Complete Guide to Home Canning ~Link~ Advises NOT to can with this method
- Penn State Collefe of Agricultural Sciences ~Link~ Advises NOT to can with this method
The SAFE METHOD OF "Canning" Dry Goods:
Use a Foodsaver with a jar sealing attachment AND oxygen absorbers together to "Seal" jars containing dry ingredients with less than 10% Moisture.
A foodsaver alone will vacuum seal the contents of a jar, but by adding an oxygen absorber a substantial amount of remaining oxygen will be removed thereby reducing the risk of mold.