Low Sugar Mirabelle Plum Jam

After a Jam Session

Recipe by Robin

Yellow plums and apricots seem similar, but they’re nothing alike to the food preservationist. True, they both belong to the Prunus genus and can be hybridized into such oddities as apriplums, plumcots, pluots, and apriums. But plums have more sour flavor components, thicker skin, and lots more water than apricots. Many plums also have less pectin than apricots. So tweaking my apricot jam recipe to preserve our Mirabelle plum tree’s bountiful harvest has been challenging. At last, after 3 years of experimentation including large batches that did not gel, batches that gelled too much, and over-sweetened batches, here is the perfected low sugar plum jam recipe.

Beginning the Jam Boil

The main difference in plum vs. apricot jam-making is that plum jam needs to cook longer. Plums contain more liquid and more air, both of which add to the cooking time as they boil down. Discarding all of the juice that comes out of the plums as they are cut up would decrease this time. However, the juice makes up a significant portion of the plum and provides the sweet flavor that marries deliciously with the sour flavors of the skin and flesh. Including the juice means that less sugar is needed. So the 45 - 60 minute cooking time is a good investment, resulting in fuller and richer plum flavor.

Use a Large Pot to Prevent Boil-Over

The second difference in preparation of plum vs. apricot jam is that since the skins are tougher and more resistant to cooking, cutting them into smaller pieces is advisable Again, to discard the skins is to discard flavor. Skins also provide much of the plums’ pectin—essential to the gelling process. Cut the skins into ½ inch pieces for best texture.

Avoid using all over-ripe plums for jam. Use about ¼ less ripe (harder) fruit as well as the super-ripe. The greener fruits provide pectin, which is lacking in softer plums. Plum jam is all about balancing sweet and tart. This recipe provides a place to adjust the sweetness to compliment your particular batch of plums perfectly.

This recipe is written for Mirabelle plums. If you use another plum variety, cook times may vary but general instructions apply. As with my other jams, I recommend allowing the fruit, sugar, and lemon juice to combine flavors at room temperature overnight in a nonreactive container. Happy Preserving!

Wipe Rim After Filling Jar

Low Sugar Plum Jam

Makes 8 half-pint jars

8 lbs. yellow plums (Mirabelles if you can find them)

2¼ lbs. evaporated cane juice (unrefined sugar)

1/3 cup fresh lemon juice

Wash and cut up plums. Cut skin into ½” squares or smaller pieces. Place both liquids (juice) and solids in a large non-metal container. Add sugar and lemon juice. Cover loosely and allow to sit in a dark, cool room overnight. You may store fruit like this up to 2 days, but if it’s longer than overnight refrigerate it and leave lid slightly ajar to avoid fermentation.

The next day: Clean and dry 8 canning jars plus a couple of extras. Invert on kitchen towel in canning area. Place 10 clean lids and rings in a bowl and cover with hot (not boiling) water.

Fill canning pot with water for processing filled jars. Preheat the water bath by bringing water to boil, then turning off heat.

Place two saucers in the freezer. You will use these to test for the gel point, the point at which you stop cooking and start canning.

Macerate the fruit by mashing it with a potato masher. Add plum mixture to a heavy, deep 8-quart stainless steel or enamel pot, including out all sugar that has sunk to the bottom. Remember that fruit will foam up during the cooking process, so make sure the pot is large enough. Bring fruit to boil, stirring occasionally.

Meanwhile, assemble your canning supplies: oven mits, large wooden stirring spoon, spoon rest, 1-cup measure or other spouted cup, canning funnel, magnetic lid lifter, high heat spoonula or spatula, two-piece digital thermometer, jar lifter, and jar wrench.

Boil the mixture on a high heat, stirring constantly. At first, plums will foam up, so monitor heat carefully and continue stirring to avoid boil-overs. Once air is released and fruit stops foaming, you can taste the jam for sweetness. If you want to add sugar, remove mixture from heat and quickly stir in sugar ¼ lb. (4 oz.) at a time. One dose, or two at the most, should do it.

Continue stirring and heating until no foaming occurs and mixture starts to get thicker and glossy. This will take about 45 minutes (different types of plums might make timing vary). Put on oven mits and long sleeve shirt when mixture thickens to avoid hot splashes.

Start testing for the gel point. Remove jam from heat. Take chilled saucer out of freezer and drop a blob of hot jam onto saucer edge. Return to freezer for a couple of minutes, until cool. Hold saucer vertically and observe jam as it runs down the plate. If it runs quickly in rivulets it’s not ready. If it moves slowly in a unified blob, it’s ready. Test about every 5 minutes until it gel point is reached.

Remove jam from heat and set on hot plate in canning area. Place canning funnel in jar and fill jar using a measuring cup or other spouted cup. Fill to ¼ inch from the top. Wipe it the jar rim and threads with damp kitchen or paper towel. Fish a lid out of the water with a magnetic lid lifter, shake off the water, and place on top of jar. Screw on ring gently, leaving it barely finger-tight. Air will need to escape the seal during processing.

Repeat with other jars until you run out of jam. Scrape the last bits from the pot with the high heat spoonula or spatula. Do not process the last jar if it’s only partially filled, refrigerate it to enjoy now.

Place jars in canning pot rack, taking care not to tilt them. Lower rack into water bath and bring to 210 degrees F, using a two-piece digital thermometer. Adjust heat to keep temperature consistent, and/or monitor pot to keep temperature low enough to avoid jam boiling out of the jars. Process for 5 minutes at 210 degrees F. Remove pot from heat and let cool 5 minutes.

Remove jars from water bath using a jar lifter and oven mit, being careful not to tilt. Tighten rings—a jar wrench helps with this. Set jars on kitchen towel—never directly on cold surface. Allow to cool and set up overnight, or for several hours.

Enjoying Mirabelle Plums Throughout the Year