How to Can Fruit Jam
Preserving jam does take some work – including spending some time in a warm kitchen filled with steam from a large kettle of boiling water – but the end result is worth the effort.
Safety is an important consideration when canning any food. If canned items are not processed correctly, bacteria can grow in the jars and produce potentially fatal botulism. Don’t let that fact scare you away from canning; just give it proper respect. Use good-quality produce, keep everything clean, and follow recommended guidelines for processing foods.
Jam should be canned when the fruit is at its peak of freshness. This usually means within a day of being picked. Always use good-quality fruit. Canning is not the way to use up fruit that is overripe. A few small bruised spots are fine; just cut them off. However, fruit that is mushy or moldy should not be used, even if the bad spots are removed.
Fruit jam is high in sugar, which helps preserve food, and can be safely canned in a large covered kettle filled with boiling water.(Open kettle canning is not recommended.) Canning kettles are very large and deep and usually come with a wire rack for holding glass jars. Lifting the rack is the easiest way to remove the jars from the kettle of boiling water. A special tongs for grasping jars from the top also is very handy. You also will need normal kitchen utensils such as spoons, bowls and measuring cups.
Ingredients needed include fruit, sugar (lots of it), pectin (for creating the gel) and depending on the recipe, lemon juice.
When choosing containers, skip the old mayonnaise jars. Use jars specially made for canning, such as Mason or Ball brands. These are durable jars with threaded necks that mesh correctly with screw-on canning bands that go over self-sealing lids. The heavy glass stands up well to the heat of canning, and seals are typically better. Antique jars with wire bails and glass tops are quaint, but they are not safe. Neither are one-piece screw-on lids. Both of these containers use a separate rubber ring, but they are not recommended because they often fail to seal properly. Canning lids have a gasket compound on the underside of the lids. When the jars are processed, heat makes the compound soften and stick to the top of the jar. When it cools, an airtight seal is formed.
Mason-type jars are available in sizes from half-pint to half-gallon and come in standard or wide-mouth varieties. For jam, you will want to use half-pint or pint-size jars. Most canning kettles will hold about eight pint-jars. Canning jars can be reused many times. The lids must be replaced after every use. The screw-on bands can be reused, but should be replaced if they become rusty. Prevent rust from forming on your bands by removing them before your jars are stored. The bands do not have to stay on the jars; the lid forms the seal.
Wash your jars and lids by hand in hot water and detergent and rinse well, or run them through a dishwasher. Then place the jars and lids in a pan of steaming hot water while you are preparing your fruit. It is not necessary to sterilize the bands. Fill your canning kettle half-full with water and put it on the heat. It takes a while for that much water to come to a boil. After it has come to a boil, keep the water at a simmer until you are ready to put in your jars.
While the water is coming to a boil, wash the fruit and remove skins, pits or stems. Chop or mash it, but don’t puree it. Jam contains chunks of fruit. Measure all ingredients carefully and don’t cut down on the sugar. The full amount is needed to ensure gelling.
Place the prepared fruit and lemon juice into a saucepan. Gradually stir in the pectin and bring the mixture to a full boil, stirring constantly. Add the sugar and continue stirring as you bring the mixture to a full boil. After it has come to a rolling boil, continue to boil for one minute. If foam forms, simply skim it off with a spoon.
Ladle the cooked jam into the hot jars. Fill almost to the top, leaving only about one-quarter inch of head space. Use a clean, damp cloth to wipe any spills from the sides and around the threads of the jar. Place the lids on the jars and firmly screw the bands onto the lids. Twist until resistance is met but don’t over-tighten.
Now place the jars in the rack and lower the rack into the canner. The water must cover the jars by one or two inches. Bring the water back to a full boil and boil with the cover on for ten minutes.
After ten minutes of boiling, lift the jars from the kettle and place them on a towel on a table or countertop. As the jars cool, you will hear the lids popping to form a seal. Sometimes this happens within minutes, sometimes it will take hours. After 24 hours, test the seals by pushing down on the middle of the lid. If it does not flex, it is sealed. If it moves, the seal did not take and the jar must be either reprocessed for the full ten minutes or simply refrigerated and used right away.
Don’t be concerned if your jam looks runny. It can take up to two weeks for it to set properly.
Remove the bands and store the jars of jam in a cool, dark place for up to one year. When you are ready to use or give away the jam, put the band back on to hold the lid in place.
Following are the ingredients and yield (in 8-ounce jars) for some fruit jam recipes. In addition to the ingredients listed, all recipes also require one package of pectin.
Strawberry: 5 cups strawberries, 7 cups sugar, 1/4 cup lemon juice. (8)
Strawberry-rhubarb: 2 cups strawberries, 2 cups rhubarb, 5 �½ cups sugar, 1/4 cup lemon juice (6)
Peach: 4 cups peaches, 5 cups sugar, 2 T. lemon juice (6)
Blackberry or raspberry: 5 cups berries; 7 cups sugar (8)
