Easy Plum Jam

The old-fashioned flavor of plum jam is one that is hard to find in stores. Making your own is EASY and a great way to preserve the harvest!

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Prep Time: 20

Cook Time: 15

Processing Time: 10

Total Time: 45

Servings: servings

Author: Kris Bordessa, National Geographic author

Prepare the calcium water: Combine ½ teaspoon calcium powder (from the small packet in the box of Pomona’s pectin) with ½ cup water in a small jar. Screw on a lit and shake until well-combined. You'll have more than you need for this recipe. Store the excess in the refrigerator for use in making additional jam or jelly recipes.
Wash the jars you'll use, making sure each is clean and free of nicks in the rim, which could impede sealing.
Wash the lids and rings in hot soapy water. (If you're using non-Ball brand lids, prepare as suggested by manufacturer.)
Place empty jars in a canning pot or large stock pot with enough water to cover by an inch or two, cover pot, and set on high heat. It can take awhile for the water to heat, so get it started before you begin making the recipe.

Measure mashed plums into a large pot along with 8 teaspoons of the prepared calcium water and lemon juice.
8 cups mashed plums, 8 teaspoons calcium water, 1/2 cup lemon juice
In a separate bowl, combine the sugar with 6 teaspoons pectin powder (the large envelope) until thoroughly combined.
2 cups sugar, 6 teaspoons pectin
Bring plums to a full boil. Add sweetener, stirring vigorously for a couple of minutes to dissolve the pectin. Once returned to a full boil, remove from heat.

Ladle hot plum jam into half-pint jars to within a quarter inch of the rim. A canning funnel makes this easy.
Wipe jar rims to remove any jam that may have spilled. A clean rim is essential to a good seal.
Set jar lids in place. Screw bands on finger tight.
Use a jar lifter to gently submerge jars into hot water in canning pot. Water should cover the top of the jars by an inch. The water will cool somewhat in reaction to the addition of the jars. Return the water to a low boil and then set the timer.
Process in a boiling water bath for 10 minutes. Add a minute to the boiling time for every 1,000' above sea level.
Check seals. Lids should be solid and pulled down tight. (if they flex and pop, the jar didn’t seal; put unsealed jars in the refrigerator and use those first).
Remove rings and wash outsides of jars. Store in a cool, dry place.

Recipe yields 8-10 half-pint jars.
This recipe is made using Pomona’s Universal Pectin. This is the only pectin I use anymore as it allows me to use much less sweetener. The standard pectin brands use an obscene amount of sugar in my opinion, often requiring equal amounts of sugar and fruit! This product uses a low methoxyl method and calls for using two different ingredients, which are included in the box: pectin (the large packet) and calcium powder (the small packet).
There are a number of ways to “mash” the plums. The easiest by far is to remove the plum pit and pulse the plum halves in a food processor.
You can also cook the plum halves until softened, then mash with a potato masher. Alternatively, run the cooked plum halves through a food mill. This will help eliminate bigger chunks of skin and pulp.
This recipe can be made using quarter-, half-, or pint jars.
Boiling lids or heating above 180°F as once recommended can damage the sealing compound.
As made, this recipe tests at about 3.5 pH.
SOURCE: Adapted from Pomona's Universal Pectin.