If you have more plums than you can eat, make jams out of them.You can keep properly canned plum jam for several months before it spoils.
Step 1: Put the plums in a container.
Remove any surface debris with your fingers after rinsing the plums.You should remove any stems, leaves, or other contaminants from the plums.Throw out any fruit that is soft.You should only use plums that are fresh and ripe.
Step 2: Blanch the plums.
Bring a large stockpot of water to a boil over high heat, then quickly dunk the plums in the boiling water.Transfer the blanched plums to the large bowl of ice water using a spoon.If you plan on removing the skins, you only need to blanche the plums.If you want, skins can be included in the jam.
Step 3: Remove the skins.
You can remove the skin from the fruit by pinching it between your fingers.You should be able to remove the skins without difficulty if the plums are ripe.Unripe plums may need more time to be blanched.
Step 4: Cut the plums.
Pull the plums out of the pits with a spoon.Cut the plums into small pieces.If you chop up the plums, discard any brown spots.If you prefer the jam to be chunkier, you could grind the fruit or chop it into smaller pieces.
Step 5: Put the plum pieces in a container.
Add the lemon juice to the plum pieces in the mixing bowl.Put the plums in a bowl with lemon juice.The lemon juice will help prevent the plums from turning brown as you work.
Step 6: The plums should be placed in a stockpot or large saucepan.
Place the plums in a pot and cover them with water.The pot should be on the stove.The plums will not burn if the contents of the pot are stirred.You can use up to 1 cup of water for thinner jam.The jam could be prevented from setting properly if too much water is added.
Step 7: The plums should be cooked for 5 minutes.
When the water reaches a full boil, reduce the heat to medium-low and cover the pot.Allow the plums to cook.It will take 5 to 10 minutes for the water to reach a boil.After the "full boil" stage has been cleared, reduce the heat.
Step 8: The butter and sugar should be added.
The butter should be put into the pot with the sugar.The contents should reach a full boil if the heat is turned back up to medium-high.The plums will not burn if the pot is left uncovered.It is optional to use butter or margarine.Adding it can help reduce the amount of foam, but if the mixture hasn't developed much foam by this point, the butter probably won' t be needed.
Step 9: Pectin can be added.
As soon as possible, add the pectin to the pot and stir it into the mixture.The entire mixture should be boiled for an additional minute.During this final minute, keep stirring the contents of the pot.You should use a metal spoon to skim off foam.You don't have to use a cooking thermometer to test the jam, but if you do use one, it will need to be at least 220 degrees Fahrenheit.
Step 10: Try the jam.
The consistency of the jam can be tested with an ice-cold metal spoon.The jam should be cool on the spoon.While testing the jam, remove it from the heat source.The metal spoon needs to be submerged in ice water before it can be used.Wait until the mixture cools off on the spoon.The jam is ready to use and can be used.If the jam is still too thin, boil it for another minute.
Step 11: The jars and lids should be sterile.
The jars and screw bands should be washed in hot, soapy water.Allow the jars, bands, and flat lids to soak for at least five minutes after pouring boiling water over them.If your dishwasher has a "sterilize" setting, you can wash the jars in it, but they should still be washed by hand.You can prepare the jars after the jam is finished, but if you want to improve efficiency and reduce the total amount of time, you may wish to sterilize jars, lids, and bands.
Step 12: The canner has hot water.
The canner should be filled with water.Allow the water to reach a full boil by setting it on your stove.You can use a large stockpot if you don't have a boiling water canner.Before boiling the water, place a metal rack at the bottom of the stockpot.The glass canning jars should not come into direct contact with the heat source.
Step 13: The jam should be ladled into the jars.
The empty head space at the top of each jar should be filled with plum jam.After filling the jars, wipe away any spilled jam using a clean, damp towel, then secure the lids and screw bands over the top of each jar.You will only need about four of the 500-ml jars.No matter the jar size, leave the same amount of headspace.The jam cannot expand or crack the glass jars.
Step 14: The jars should be placed in the boiling water.
To lower the jars into the canner, use jar tongs.Keep at least 2 inches of space between the jars to prevent them from hitting each other.There should be at least 1 to 2 inches of water on top of the jars.If you don't have enough water in the canner, you should add more boiling water.
Step 15: 5 to 15 minutes is how long it takes to process.
Depending on your altitude, process the jars of jam for 5 to 15 minutes.The water should be boiling throughout the time.For altitudes between 0 and 1000 ft, process the jars for 5 minutes.For altitudes over 6000 ft, process the jars for 10 minutes.For altitudes over 6000 feet, process the jars for 15 minutes.The processing times should remain the same for both jars.
Step 16: The jars should be kept cool.
The jars of jam need to be removed from the water.Allow them to cool down on a cloth-covered surface.Make sure the jars don't hit the canner on the way out.If this happens, the glass may break.It will take a long time for the jars to cool.Depending on when you started the process, you may need to wait overnight.
Step 17: The seal should be tested.
The seal can be tested by pressing the button at the center of each lid.When pressed, the button should not move.The seal should be tested on each jar.Don't assume that all seals are secure just because the first two seem secure.You can use the jam within a few weeks if the jar has been sealed correctly.If you don't want to use any jam immediately, you could try to reprocess it by placing a new jar with a different lid.
Step 18: Store the jam.
After labeling the jars with their contents and the current date, store the jam in a cool, dry, and dark place for 6 to 8 months.You can use plum jam within three weeks if you store it in your refrigerator.