We've finished canning the plum jam. It's amazing how you can take a dark blue fruit with green pulp and end up with a beautiful plum colored jam!
The chopped plums, sugar and lemon juice sat for two hours while the juice flowed from the pulp. We put it on the stove top and brought it to a rolling boil. Elegante Mother skimmed the foam from the top, and I worked on getting the jars ready for the canning.
As the jam was cooking, I asked EM if leaving the skins of the plums in the jam wasn't a bit odd. She said "Yes!" so that sent me scurrying for our copy of "Stocking Up."
I didn't find the definitive answer to whether the plums should be skinned prior to cooking or not, but I suspect that the pulp needs to be cooked with the skins in order to develop the color and the pectin needed to jell.
So, I got out the food mill. When the jam had cooked for 30 minutes, I took small batches and forced it through the food mill, separating the pulp from the skins. By the time the utensils were scraped off and the pulp had been canned we had six four ounce jars of jam plus most of a seventh.
The jam is a bit runny, and a gorgeous deep reddish purple. It's tart, with a lot of intense plum flavor. Although I wish we had produced more jars of jam for the effort, I think the taste is going to make it all worthwhile.
If I can find the larger Italian purple plums, we might have another go at jam making, but you can bet I'm going to surf on the subject of what to do with the skin!