Many people replace vacuum sealing or oxygen absorbers
with this storage prep method, but is it really safe?
Dry oven canning is the process of canning dry goods (such as flour, beans, oats, and dehydrated foods) in a 200°F/95°C oven. The standard instructions are to place items in glass canning jars, wet the rim of the lid a bit, place lid and ring on top, and then allow the jars to remain in the oven for about an hour.
The premise is that this is a way you can extend the life of dry goods even in a scenario in which you have no electricity (in a solar oven, or even in a car on a bright sunny day). However, this method is not only bad for your food, but unsafe. Consider these reasons why…
- The key enemies of successful food preservation are heat, light, air, and vermin. So starting the life of your food that you intend to have on a long-term basis with deliberate heat is not a good idea. Also, this method commonly encourages the wetting of the rim. Since moisture is one of the enemies of long-term shelf stability, this will not work.
- For foods that are vulnerable to going rancid over time, even in cooler storage conditions, an hour in the oven at 200°F/95°C reduces the standard shelf life of your foods to approximately 50% with such a choice. For example, brown rice (challenging to store long term because of its Omega fats) will actually go rancid 50 times faster than merely storing it in your cupboard in its original packaging.
- An hour of heat exposure comes with a heavy price when it depletes valuable nutrients. The oven canning method has the ability to convert what would otherwise be a valuable nutrient source into an empty calorie source when exposing some foods to this kind of process.
- The usual method of 200°F for an hour is intended to heat up the ingredients inside the jar, as well as the jar, in order to kill any germs and to cause a seal of the lid to the rim. But that formula will vary greatly depending on the density of what you’re sealing, a concept that has not been taken into consideration.
- In addition, the oven canning process does not actually EXPEL all of the oxygen from the jar like vacuum sealing does. Instead, you’re storing your dry goods amidst the oxygen that remains in the jars. Heating the contents plus the lids doesn’t solve the oxygen problem, whereas vacuum sealing does. The seal may be airtight when you’re finished with this method, but the oxygen is still inside.
And the MOTHER of all reasons? Oven canning is just not safe.
- Jarden, the manufacturer of Ball, Kerr, and Bernardin canning Mason jars, has given their official position (phone number: 800-240-3340). Heating jars in the oven for canning, dry canning, or using jars to bake is unsafe and not recommended. The jars were not made for this purpose. The unsafe condition is what is called Thermal Shock Breakage. The heat from an oven is a DRY heat, different than what is produced in a water bath or pressure canner. The breakage can occur during the heat process inside the oven or outside on the counter as they cool. This breakage could be anything from a crack in the glass where shards may be deposited into the jar and not observed by the preparer ending up in your food, to a full exploding break of the jars.
As I often tell people, “Food preservation safety is like pregnancy…it only takes ONE TIME.” People DO DIE from food poisoning and accidents such as this”
National Center for Home Food Preservation; Is it safe to process food in the oven?
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