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Spoonful of plum jam sits atop an open jar of the jam. Vampire Red Plums and biscuits topped with the jam are in the foreground while jars of the jam form the backdrop

Red Plum Jam

This Red Plum Jam is a fabulous way to preserve one of autumn’s best fruits. With its rich dark color, this jam has a lovely balance of tartness and sweetness. Enjoy it on toast, scones or biscuits.
Course Jam
Cuisine Canadian
Keyword homemade jam, jam, Plum Jam, Red Plum Jam, Tips for Jam-making
My Island Bistro Kitchen My Island Bistro Kitchen - Barbara

Ingredients

  • 3 lbs/1.3kg ripe red plums suitable for jam making (e.g., Vampire Red Plums variety), pitted and quartered or coarsely chopped
  • 1½ lbs/680g granulated sugar
  • ½ cup water
  • ¼ cup bottled lemon juice
  • 1½ tsp butter

Instructions

Preparing the Plums:

  1. Wash plums. Cut in half. Remove and place stones in small saucepan. Cut plum halves (unpeeled) into half again with larger plums cut further into smaller bite-sized pieces. Place cut-up plums into large bowl.

  2. Add ½ cup water to the plum stones in the saucepan. Cover and bring to a boil over medium heat then reduce heat and simmer for approximately 10 minutes or until stones have all cleaned off of any fruit bits. Stir occasionally. Strain out and measure ¼ - 1/3 cup of the plum liquid. Cool slightly then add strained plum liquid to the cut up plums. Discard the stones and any remaining liquid.

  3. Stir the sugar into the plums and gently mix well. Cover bowl with plastic wrap and place in refrigerator for at least 6 hours, or overnight, to allow the fruit to macerate. Stir a couple of times during this process.

Preparing and Sterilizing the Bottles:

  1. When plums are nearing the end of the maceration time, prepare the bottles and hot water canner. Wash jars and lids in hot soapy water, first checking to ensure that the jars have no cracks or chips in them. Rinse well and drain. Fill a large pot about half full of hot tap water. Place a wire rack on bottom of pot to hold jars. Place the jars, upright, into the water. Ensure the jars are fully submerged, each jar filled with water, and add more hot tap water as necessary to ensure that the water is at least an inch over the tops of the jars. Cover, bring to a boil, and boil the jars for 10 minutes. Turn off heat and leave the jars in the hot water to have ready to fill once the jam finishes cooking. Examine screw bands to ensure there are no dents or rust.

Preparing the Canner:

  1. Once the jam is underway on the stove, fill the canner about half full of hot tap water. Cover and bring to a boil to have it ready for processing of the filled jars as the jars filled with jam must immediately go into the canner to be processed while the jam is still hot. Ensure the canner water is boiling before the jam has finished cooking as there will not be enough time to get it to the boiling point once the jam is in the bottles and ready for immediate processing. As the jam is nearing the end of its cooking, boil a kettle of extra water to have ready, if needed, to top up the canner water after filled jars are added.

Making the Jam:

  1. Place macerated plums (do not drain) in medium-sized stock pot. Add lemon juice and butter. Stir well. Cook, uncovered, over medium heat until mixture reaches 218°F - 220°F on a candy thermometer or instant read thermometer, stirring frequently and skimming off and discarding any foam that appears. Stir more frequently as jam thickens and gets closer to 218°F - 220°F to prevent it from sticking to the bottom of pot and scorching. Reduce heat slightly if jam boils too fast. Keep jam at a good steady moderate boil, but not boiling vigorously. Remove jam from heat while testing temperature as this will give a more stable reading than testing it on the heat. Once jam has reached 218°F - 220°F, immediately remove stockpot from heat and skim off and discard any residual foam from the jam.

  2. If a candy thermometer or instant read thermometer is not available, place 2-3 freezer-safe saucers in freezer. When jam has reduced and thickened well, remove pot from heat and place a small amount of jam on chilled saucer and slightly ‘tilt and swirl’ saucer around to distribute the jam to determine if it has set. Let jam sit, untouched, for about a minute, then gently push your finger through the jam. If the jam holds its shape (i.e., does not immediately run back together after the finger has been removed from the jam), it is set and ready to bottle. If not, continue to cook mixture, repeating the “chill” test about every 3 – 5 minutes or so (always removing the pot from the heat while conducting the chill test) until the jam passes the “chill” test.

Bottling the Jam:

  1. Use jar lifter tongs to carefully remove the hot sterilized jars from the water, one at a time, emptying the water from the jars back into the pot. Drain jars well.
  2. Using a ladle, or a heat-proof glass measuring cup, and a wide-mouthed canning funnel, transfer jam into the hot sterilized jars, leaving about ¼“ headroom in each jar to allow for expansion during the hot water processing. Remove any trapped air bubbles in the jars with a chopstick or small heatproof, non-metallic spatula. Wipe the jar rims with a clean damp cloth to remove any stickiness or jam particles that could prevent the lids from sealing properly to the jars.

Hot Water Processing the Jam:

  1. Using jar lifter tongs, carefully place filled jars upright in wire basket positioned in the canner, ensuring jars do not touch each other or fall over. If canner is not filled to capacity with jam-filled jars, fill up empty spaces with hot empty jars to prevent the filled jars from toppling during the hot water processing. Ensure the water level is at least 1” above the tops of jars, adding more boiling water as necessary. Cover with canner lid. Return the water to a full rolling boil over high heat then decrease the heat to just keep the water at a moderately rolling boil but not boiling over. Process jars in the hot water bath for 10 minutes, adjusting time as and if necessary for altitude. Start timing the processing from the point at which a full rolling boil is reached after jars have been added to the canner. At the end of the processing time, turn off heat and remove canner lid.

  2. Let jars sit in the hot water for 5 minutes then, using jar lifter tongs, carefully remove the jars filled with jam, upright and one at a time, and transfer them to a wire cooling rack set on a heat-proof board to cool completely. Listen for the “pop” or “ping” sound as the bottle lids seal over the next few minutes or hours. The lids of properly sealed jars will curve downward. Let jars rest, undisturbed, on counter for 24 hours. Then, test each jar for proper sealing by pressing down gently on the center of each jar lid. If the lid is already pressed downward, and does not pop back up, it is properly sealed. Any jars that do not pass this test should be refrigerated and the jam used within a week or so. Store properly sealed jam bottles in cool, dark place. Refrigerate jam once jar has been opened.

Recipe Notes

Yield: Apx. 4 half-pint bottles and 1 quarter-pint bottle

(Copyright My Island Bistro Kitchen)

NOTE: Because so many factors can affect yield (e.g., quality of plums, variety, and how much the jam is cooked down), it is difficult to say, with certainty, the exact yield. That said, four (4) half-pint bottles and one (1) quarter-pint bottle have been the consistent yield from the recipe developer’s testings. However, it’s a good idea to have a couple more bottles ready and sterilized in case yield is greater. It’s also good to have a couple of extra bottles heated to use, if needed, as empty vessels to fill the canner to its capacity to prevent filled jars from toppling over during the hot water processing.