Can i sterilise my filled jars of marmalade, raspberry and cherry jam in a steamer unit, such as those used to steam vegetables or baby bottles? I usually make batches of 15 jars so its difficult for me to double boil them all.
1 Answers
The key issue is getting the contents of each jar up to the requisite temperature for the necessary time, all the way through to the center of the jars. It would be conceivably possible to use steaming to do so, if the requisite controlled temperatures and times could be regulated, and appropriate recipes developed.
However, according to the USDA as reported at the National Center for Food Preservation:
Steam canners are not recommended because processing times for use with current models have not been adequately researched. Because steam canners do not heat foods in the same manner as boiling-water canners, their use with boiling-water process times may result in spoilage.
If purpose built steam canners are not recommended, I would strongly urge you not to improvise with other devices.
You should only use recipes and methods for canning that come from highly reputable sources, such as a University Extension.

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Note though that steam-canning itself hasn't been proven ineffective. Just not enough research has been done on it to determine safe processing times. If you're not using a pressure canner, a boiling water version is usually very affordable at your local supermarket or hardware store. If you really want to steam process, do more research and find tested recipes. If going with boiling water, get a pressure canner anyways. You can boil in a pressure cooker, but you can't pressure cook in a boiling pan. – JSM Aug 19 '14 at 20:49