Pressure canning is not a suitable method for processing jam & jelly. Because pressure canning produces very high heat, there is too great a risk of breaking the pectin down. When the pectin gets broken down, either you get no jell at all or an inadequate jell.
The USDA does not publish any guidelines for successfully pressure canning jam & jelly, so we do not endorse that way of processing jam & jelly.
The water-bath method is the most tested and most reliable method for canning jam & jelly.
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Posted in: 6. Questions About Jam-Making Equipment and Water Bath Canning