There's no organization I know of that has scientifically verified convection oven canning. Without verification I wouldn't trust either my head or my gut because there's just no data.

A lot of people think if there's heat and the lids suck down or "ping" it's the same as canning and it's not. Jars can seal without a full vacuum. And any oven of any sort is dry heat which doesn't have the same thermal qualities as moist heat. Ovens and boiling water bath aren't comparable.

Having said that, if they're sealing jelly in a convection oven, I personally wouldn't get too worried about it. Not because convection has particular merit but because jelly is so inherently low-risk it's just not a concern. The worst that would happen is a failed seal or inadequate heat penetration and mold.

But if they're putting jars of tomatoes in there, I hope you can convince them it's a risky practice.

Carol

Carol,

Thanks for your reply. I needed expert confirmation of what my gut told me.

Bill

Oven procssing be it convestion or other, is not safe as it will not give each jar the same heat penetration, even if there is a fan inside. I don't know what temp they processed at, but an oven would be very difficult to hold a temp at 212 degrees, of boiling water. Going any higher can rupture lids and cause boiling inside the jars, under 212 its not high enough to resist spoilage. I wouldn't eat any of their canned stuff!

Thanks Ken,

No, we donÂt eat their preserves we have enough of our own (safe) stock.

Bill

Just to second what Carol said, the heat transfer from air to a solid is much less efficient than heat transfer from water to a solid. Convection from water is really great for heat transfer, which is why some grocery stores have those swirling ice water baths to chill wine much faster than just putting it in front of the cold air vent in the freezer. So for the same canning time, the convection oven will do much less heating of the jar and contents.

The only safe type of convection canning is convection from boiling water or steam.

Plus, as Ken alluded to, using a higher temperature could cause the jars to crack. You have the same problems as regular oven canning, except probably more dangerous because the heat transfer is more efficient with the convection oven (but still much less efficient than water).

Melissa

I agree, this is not a safe practice. All for the reasons given. Those jars are not approved for oven use. The company that makes the canning jars will tell you that. They can shatter and cause injury.
Besides, who wants to do this and risk losing your jam after all the time and ingredients. They can mold still or ferment. Molds cause mycotoxins that cause certain cancers. So, you can't just safely scrape off the mold. Especially since what you see on top is just the tip of the iceberg. Tons of mold spores all through moldy jam.

I agree with discarding moldy jam. However, while there's a correlation between mycotoxins and cancer, cause has not been established. I don't think we should overstate.

Carol

All this conjecture about whether convection canning jam/jelly is safe or not cracks me up.

Water bath processing doesn't produce any better of a vacuum than oven processing or for that matter no processing -- the hot liquid itself produces a seal just fine. The question of vacuum seal totally misses the point and is totally irrelevant. A vacuum means a space devoid of anything, and not only do canned jars have air in them (regardless of how you process them) but also food and, yes, plenty of bacteria (though less than you had before processing of course).

Processing just reduces the bacteria inside the jar to an acceptable level, that's all. Depending on the product you're canning, no processing whatsoever might be just fine (e.g. high acid, high sugar jam/jelly). On the other hand high temperature processing with a pressure cooker might be essential (e.g. low-acid tomatoes, meat, beans).

The question was: can you can jelly with a convection oven (safely). And the answer is (as Carol pointed out): yes.

For a different perspective on alternate processing methods see:

http://www.hillbillyhousewife.com/oven-canning-method.htm

Yes, you can even can tomatoes without heat processing if you use salicylic acid as a preservative. Salicylic acid is a relatively harmless preservative and the benefits of not processing include better taste and improved nutritional quality:

http://www.bobthechef.com/step-by-step/canning-whole-tomatoes

Of course we need to go a website that comes from a country undominated by the USDA spectre :) The USDA pooh-poohs salicylic acid of course.