This week we’re featuring fruit recipes, because we had a ton of leftover fruit in the house! My 18-year-old daughter Abby threw a 4th of July party, and apparently she thought the occasion called for buying massive quantities of red and blue berries. Once the party was over, I realized I had a great opportunity to make my favorite low sugar blueberry jam.
Making homemade jam is pretty easy, but you will need a little bit of canning equipment:
- Water bath canner with canning rack
- 1/2 pint Mason jars with lids and rings
- Jar lifting tongs
- Canning funnel
- Magnetic wand for retrieving lids from hot water (optional)
You can find the jars, rings, canners and all the equipment at stores like Walmart or many grocery stores, or you can order a canning kit, like this Ball Enamel Water Bath Canner with Utensils, from Amazon. Most people only have to buy this equipment once, and it lasts a lifetime. The one exception is the jar lids and rings, which have to be replaced.
You will also need some of your regular kitchen equipment for this recipe:
- Potato masher
- Large, open pot, like a soup pot, for boiling the jam
- Wooden spoon or heat-proof silicone spatula, for stirring
- Large spoon for skimming
- Large liquid measuring cup
- Dry measuring cups and spoons
- Small ceramic plates
- Clean kitchen towels
Before you begin, inspect and wash 6-7 half-pint Mason jars. Run your finger around the rim of each jar to make sure it’s not chipped. A chipped jar won’t seal properly. After you inspect the jars, wash them in the dishwasher, or by hand with hot soapy water. Set the clean jars aside on a drying rack or clean kitchen towel.
Our mothers and grandmothers used to sterilize jars by boiling them for 10 minutes, but this isn’t necessary. The jars will be thoroughly sterilized during the water bath canning process.
Once the jars are clean, put 2 small ceramic plates in the fridge, because you will need those later for testing the jam.
Next, wash about 8 cups of fresh blueberries, and pick out any stems that might be sticking to them. Eight cups of fresh blueberries should yield 5 cups of mashed blueberries, which is what you need for this recipe.
You can mash the blueberries with a potato masher, or process them in a food processor using a pulse setting. For this jam, I mashed the blueberries with a potato masher, but later I thought the jam was too chunky, so during cooking I blended it a little bit with an immersion blender.
A key ingredient to low sugar jam is low sugar pectin. You can usually find this in grocery stores near where the canning supplies are. Pectin helps the jam thicken. Make sure you get the low sugar pectin and not the regular.
Low sugar pectin contains a mold inhibitor, which is needed for reduced sugar recipes. Many people don’t realize that the large amount of sugar in regular jam recipes acts as a preservative. So if you’re reducing the sugar, you need to use low sugar pectin.
This recipe simply calls for fruit, sugar, lemon juice and pectin. Mix the fruit, lemon juice, pectin and 1/4 cup of sugar in a large soup pot, and bring that to a full boil. Then add the rest of the sugar to total 3 1/2 cups, and bring it back to a full boil for one minute. A full boil, also called a hard boil, is a boil that doesn’t go away when stirred. Stir the jam the entire cooking time so it doesn’t burn.
Yes, 3 1/2 cups of sugar is a low sugar jam recipe! A regular jam recipe would call for 7 cups of sugar! Regular jam is more sugar than fruit. The way I look at low sugar blueberry jam is that it’s a lot of sugar per recipe, but not per serving. It has so much flavor that you’re not going to eat a lot at once.
You might notice that this recipe calls for less fruit and sugar than the recipes that come with your box or container of pectin. I use ratios of fruit, sugar and pectin that will make a relatively thick jam, which is what I like. This jam has a spreadable rather than a pourable consistency.
Once the jam has come to a hard boil a second time for a full minute, you can test its texture. Remove the jam from the heat, and take one of the cold plates out of the fridge. Pour a small spoonful of jam on the cold plate. If the jam thickens up to a texture you like, it’s done.
If you test the jam and it’s still too runny, boil it for another minute and test again. If it’s too runny after that, you might need to add another 1/4 box of pectin and boil again. (I’ve actually never had to do that.) This batch was perfect after the first test.
Once the jam is cooked, use a large spoon to skim off the foam. There’s nothing wrong with the foam, but it doesn’t look pretty.
After the foam has been skimmed, let the jam sit for 10 minutes or so, then stir. This will help distribute the fruit chunks so they don’t float to the top when the jam is in the jars.
While the jam is resting, get the lids ready. In decades past, Mason jar lids needed to be soaked in hot water before using. This step is no longer necessary. Just make sure the lids are clean and dust-free. I wash my lids and rings with hot water, and set them on a clean kitchen towel until I need them.
Fill the jam jars using a ladle and canning funnel. Make sure to leave about 1/4 inch of “headspace,” or empty space, at the top of the jar, so if the food expands during processing, the lid doesn’t blow off!
Wipe off the rims of the jars with a clean towel. Place the lids on the jars and secure with rings, but don’t screw the rings on too tight.
Place the rack inside the water bath canner and fill with water. Place the jars carefully in the canner. The water should cover the tops of the jars by at least one inch. Follow the directions that come with your water bath canner.
Processing time depends on how far you are above sea level, so check the recipe below. At the end of the processing time, use the jar lifting tongs to remove the jars from the water, and set them on a clean towel. Let them sit undisturbed for several hours, so they can seal. You know they’re sealed when the center of the lid is depressed slightly and doesn’t move when you press it with your finger. You might hear a popping sound when the lids seal.
Making your own jam is totally worth the effort! Homemade jam also makes a great neighbor gift. Give it a try and let me know how it turns out!
Low Sugar Blueberry Jam
For the jam:
- 8 cups whole raw blueberries to yield 5 cups mashed blueberries.
- 3 ½ cups white sugar
- 1 box low sugar pectin
- 3 tablespoons lemon juice either fresh or bottled
- 6 half-pint Mason jars with lids
- Potato masher
- Large wooden spoon or silicone spatula for stirring
- Large wide pot like a soup pot for cooking
- Water bath canner
- Canning funnel
- Jar lifting tongs
- Sterilize the jars by washing in the dishwasher on the sterilize cycle or immersing in boiling water for 10 minutes. Place clean jars on a clean towel. Put 2 small ceramic plates in the refrigerator, because you will need them later to test the thickness of the jam.
- Wash the blueberries, and pick off any stems. Mash them with a potato masher, or process carefully with a food processor to get the texture you want. Measure the sugar, and reserve ¼ cup to mix with the pectin.
- Mix the pectin, lemon juice, and ¼ cup sugar in a small bowl or measuring cup.
- Place the blueberries in a large cooking pot, and add the pectin mixture. Over medium high heat, bring everything to a full boil that does not go down when stirred. Stir the entire time so the jam does not burn. At this point, add the rest of the sugar, stir well, and bring the jam back to a full boil for one minute. Turn off the heat and test the thickness of the jam by putting a small spoonful on a cold ceramic plate. If it’s thick enough, it’s done. If it’s too runny, add ¼ package more pectin, bring to a hard boil again for 1 minute, and test again with the second cold plate.
- Let the jam cool for 10 minutes, then stir to distribute the fruit. If the jam is too hot when you put it in the jars, the fruit chunks will float to the top. Meanwhile, place the Mason jar flat lids (not the rings) in very hot (not boiling) water to get them ready.
- Fill your jars, using the ladle and funnel, leaving 1/4 inch of clearance space at the top of the jar.
- Wipe the rims of the jars with a clean, damp towel. Place the lids on the jars and secure with rings. Do not screw the rings on too tight.
- Process the jars, following the instructions for your water bath canner. This jam requires 5 minutes processing at sea level, 10 minutes above 1000 feet altitude and 15 minutes above 6000 feet altitude.
- Remove the jars carefully with the jar lifting tongs, and set them on a clean towel. Leave them undisturbed for several hours or overnight to let them seal. You can tell they are sealed if the center of the lid is depressed slightly and does not move when pressed with your finger. Remove the rings so they don’t rust due to trapped moisture, or if you want to leave them on, at least remove them temporarily to make sure they are dry underneath. The jam lasts about a year in the pantry.