Making jam does not have to be a time-consuming production. It can be as simple as cooking enough plums and sugar to fill a single jar. You don't even have to worry about fumbling with the enormous battery of equipment required for sterilizing, boiling, and sealing. The jam can go straight into the fridge, where it will safely keep for a couple of weeks. And chances are good that it will disappear well before then.
To make plum jam, you will need only three ingredients: plums, sugar, and lemon juice. I don't bother peeling the plums -- the skins impart a lovely burgundy color to the finished jam. Seek out fragrant, ripe fruits that yield to gentle pressure. If the only available plums are as hard as golf balls, just give them a few days to reach their full, tender potential. Since plums are climacteric fruits, they will continue to soften and sweeten after they are picked from the tree.
There are over 2000 varieties of plum to choose from, and 95 percent of the entire U.S. crop can be found growing in California. Reine Claudes plums, native to France, are small orbs with chartreuse skin. Also known as greengages, they are highly prized for their honeyed sweetness. Elephant Heart plums, developed by Luther Burbank in Sonoma County, have smooth yet mottled skin and ruby red flesh that bursts with juiciness. Mr. Burbank, a turn-of-the-century American botanist, also introduced the Santa Rosa plum, which remains an early-summer favorite among market goers for its rich, tangy flavor.
Once you select your favorite variety of plum, it needs only to be cooked with sugar for a brief 10 minutes. You can test the thickness of the jam using a few different methods: placing a spoonful on a cold plate from the freezer to check its consistency, watching for uniformly small bubbles in the simmering jam, or looking for the moment when the jam clings to the stirring spoon. But I tend to rely on a thermometer reading of 221ºF. Occasionally the jam turns out a little too runny despite my best efforts. Even then it is still delectable. I just call it plum sauce and pour it over ice cream!
This recipe can easily be doubled, or even quadrupled. You can adjust the amount of sugar to your taste, adding another scoop if the plums are too tart.
Makes 1 pint
1 pound plums
½ - 1 pound (1 1/8 - 2 ¼ cups) granulated sugar, depending on the sweetness of the fruit
1 tablespoon lemon juice
Without peeling the plums, slice them into wedges and discard their pits. Taste a piece of plum to decide how much sugar needs to be added. (If the fruit is sweet enough as is, add only ½ pound sugar; if the fruit is quite tart, add a bit more sugar.)
Combine the plums, sugar, and lemon juice in a wide, heavy-bottomed pot. Set aside to macerate for 1 hour.
Place the pot over low heat, and stir the fruit until the sugar dissolves. Turn up the heat to medium-high. Cook the jam at a rapid boil, stirring frequently, until its temperature reaches 221ºF (at sea level; add 2ºF for every 500 feet of elevation), about 10 minutes. Remove the pan from the heat. Carefully transfer the hot jam into a clean jar.
(This jam is meant to be stored in the refrigerator for up to 2 weeks. If you would like to seal the jar's lid and store the jam for a longer period of time, it's safest to follow a recipe intended for that purpose.)
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