Out of hand the flesh of a Japanese plum is so mild you might consider dialling back the sugar for a jam recipe. You definitely should not! First, the sugar is essential for the mixture to actually “jam” or set, but also that generous dose of sweetness balances the acidity that is unleashed during cooking. I ended up using the same ratio I use for raspberry jam: 2:1 fruit to sugar. Even with this high sugar content, the jam is quite tart. We noticed that of our two varieties, Ptitsin #3 and Ivanovka, the Ptitsin was significantly more sour than the Ivanovka after cooking. This combined with Ivanovka’s much deeper colour means Ivanovka might become our go-to cooking plum, and Ptitsin our preferred fresh plum.
Nothing novel about the process here: fruit and sugar in the pot, simmer vigorously while skimming away any foam that develops. Once the mixture reaches the proper thickness, pour into hot mason jars. One interesting thing you can do is manipulate the colour of the jam by changing the amount of plum skin you include in the mix. The skins are the source of all the red pigmentation, so if you remove them you get a jam with the colour of orange marmalade.
So, how to use plum jam made from Japanese plums? Obviously slathered on buttered toast is great. For years I’ve been dreaming about making some of the desserts of central and Eastern Europe that use plum jam, dishes like Powidltascherln (think: plum jam pirogies). The jam from our Japanese plums has turned out much different than the European version (much more tart, much lighter and brighter in colour) so they won’t be dead ringers for the European dishes, but hopefully still tasty.
- 1.2 kg pitted Japanese plums (Prunus salicina)
- 600 g white sugar
- Warm 4 x 250 mL immaculately clean mason jars in a 250°F oven.
- Combine the pitted plums and white sugar in a heavy pot on the stove. Put on medium heat. Cover and let cook until some liquid has pooled in the bottom of the pot.
- Remove the lid and raise the heat to medium-high. Maintain a vigorous simmer. Skim any foam that comes to the surface.
- Once the plum mixture reaches about 220°F, remove the hot jars from the oven. Using a canning funnel, transfer the hot plum mixture into the jars, leaving 3/8″ clearance. Ensure there are no air pockets in the mixture. Apply the lids. Let the jars stand on the counter until they have all sealed properly.
- Transfer to cellar for long term storage.
Yield: 4 x 250 mL jars plum jam