Wash and sterilize a jar, then thoroughly allow to dry.
Remove the pits from the plums and roughly chop the flesh. When cutting out the pits, be careful not to cut into them.
In a saucepan, place the chopped plums from Step 2, sprinkle with sugar and lemon juice, and let sit for about 10 minutes to blend.
Bring the saucepan to a boil, then reduce to low heat. Simmer for about 5-10 minutes while occasionally stirring to prevent it from burning.
After about 5 minutes, it will start to thicken. Once it falls off right the spatula when stirred, turn off the heat and it's ready.
Transfer to the jar while still hot. It's delicious served on yogurt.
I was told by another user that the plums will not gel. If your jam is lacking in sugar, pectin, or acid, it will not gel. This is a low-sugar umeshu (plum) jam.
If your jam is not gelling together, add powdered pectin or sugar. And be sure to not to forget the lemon juice.
Story Behind this Recipe
I make jam to use up my plums leftover from making umeshu. It's easy to make and it's packed with plenty of umeshu flavor.
For this recipe I used our family's umeshu Recipe ID: 824400, using plums from a 3-year-vintage batch. In Step 2, they can be roughly chopped as shown. They will soften and become syrupy once heated. In Step 5, if you overcook the jam, it will harden when it cools, so be careful. The alcohol will remain after cooking, so this is not to be served to children.