how to size down preserves jar - Ask Extension
Hello,I'm currently taking the food preservation course, and in one of the videos (perhaps the hot water bath section?), it mentions that you can neve...
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how to size down preserves jar #891203
Asked January 03, 2025, 11:57 AM EST
Hello,
I'm currently taking the food preservation course, and in one of the videos (perhaps the hot water bath section?), it mentions that you can never size up but can size down the jar when preparing food to be canned. I have looked and can't find information about this. My main questions are: Is there a rule of thumb about what can be sized down? Do the processing time and headspace change if the canning jam is in a smaller jar? I mostly can tomatoes and jams.
I'm currently taking the food preservation course, and in one of the videos (perhaps the hot water bath section?), it mentions that you can never size up but can size down the jar when preparing food to be canned. I have looked and can't find information about this. My main questions are: Is there a rule of thumb about what can be sized down? Do the processing time and headspace change if the canning jam is in a smaller jar? I mostly can tomatoes and jams.
Ingham County Michigan
Expert Response
Processing times are based on the recommemded jar size. Doubling the canning jar size can lower the heat penetration of the food in the jars and increase the risk of spoilage and foodborne illness, or containers. When halfing a canning recipe, use the processing time listed for the recommended jar size.
If doubling jam and jelly recipes, the quality may suffer and the longer boiling time to reduce the liquid will prevent the pectin from forming a gel.
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