Here’s a simple plum jam with just three ingredients– four, if you decide to add a dash of vanilla. I love recipes like this. Simple, classic, and incredibly delicious. The plums are naturally high in pectin, and using an appropriate amount of sugar lets them gel.
My plum jam is loosely based on the one here, from Serious Eats and The Blue Chair Jam Cookbook. My version of the recipe, below, includes the whole 5 lbs of plums and 2 lbs of sugar, but you can scale down by weight. If you don’t have a kitchen scale, no problem– just estimate the amount of plums and sugar. Try to use more, rather than less, lemon juice, if you’re estimating, to keep the pH low. The acidity of the plums and lemon juice should mean that you can can this jam, process it in a water bath, and safely store it at room temperature indefinitely, regardless of sugar content. However, if you want to be extra safe, store in the fridge for up to a couple of months. (This is what I chose to do.)
I found my plums at peak ripeness, falling off a tree in North Berkeley. Yours might come from the store. My jam was extra-tart from the fruit I used, but your may be sweeter. Taste your fruit, and add lemon juice and sugar accordingly.
- 5 lbs red-fleshed plums, pitted and chopped
- 2 lbs granulated white sugar
- 2 ounces (4 tbsp) lemon juice
- 1 tsp vanilla extract (optional)
- Place 4 or 5 stainless steel spoons in the freezer.
- In a large non-reactive pot, toss together the chopped plums and sugar. Cover and allow to macerate for 30 minutes at room temperature. (Or, refrigerate for up to 24 hours.)
- Add lemon juice. Place the pot over medium heat, stirring occasionally to prevent scorching. The jam should foam and bubble in about 15 minutes. Continue to cook until the foaming subsides, another 15 minutes.
- Then, stir in the vanilla if using. Cook the jam another 5-15 minutes until glossy. Total cook time should be anywhere from 30-45 minutes. My smaller batch came out around 30 minutes.
- Towards the end of cooking, test the jam every few minutes for doneness. Place a small, dime-sized dollop of the jam onto one of the cold spoons from the freezer. Place the spoon back in the freezer for a few moments. Once the jam is cold, tilt the spoon to see if the jam runs off. When the jam stays put, with minimal runniness, it is done and ready to be canned or cooled and refrigerated.