Start to Finish: 30 minutes, plus cooling time
Servings: 5 cups
Strawberry rhubarb jam, with its sweet-sour taste, benefits from the addition of sugar, as it makes the sourness of fresh rhubarb tolerable. However, sugar in jams, including strawberry rhubarb jam, also acts as a preservative, preventing molds from growing. Sugar also helps jams thicken and gel by reacting with pectin. Too little sugar can mean a runny jam. To ensure that a low-sugar strawberry rhubarb jam sets correctly, use a low-sugar pectin. This recipe is adapted from one by Pomona Pectin.
2 cups strawberries, frozen or fresh
2 cups rhubarb, chopped
2 teaspoons grated nutmeg
2 tablespoons fresh lemon juice
3/4 cup white sugar
2 teaspoons calcium powder
9 teaspoons low- or no-sugar pectin
Thaw the strawberries, if you are using frozen fruit, and cut them — either fresh or thawed — into quarters. Cook the chopped rhubarb in a non-reactive saucepan over medium heat. Add 1 tablespoon of water, and cook until it is soft, about 10 minutes.
Add the strawberries and cook for another 10 minutes. Add more water if needed, 1 tablespoon at a time, to ensure the fruit does not stick or burn.
Mash the rhubarb and strawberry into a thick paste with a potato masher or fork. Add the grated nutmeg and lemon juice to the fruit. Mix the 2 teaspoons of calcium powder with 1 tablespoon of water to make calcium water. Add the calcium water to the pot and stir to incorporate.
Mix the sugar and pectin powder in a bowl. Turn the heat to high, and bring the mashed fruit mix to a rolling boil.
Stir in the pectin-and-sugar mix into the fruit blend. Stir thoroughly to ensure that the pectin and sugar dissolve completely. Do this for one to two minutes.
Taste the jam to test for sweetness. Add extra sugar, 1 tablespoon at a time, until the desired sweetness is achieved. Bring the jam back up to a rolling boil for one minute before removing it from the heat and continuing.
Return the jam to a rolling boil and remove the pot from heat. Ladle the jam into sanitized glass jars. Fill the jars up to 1/4 inch from the top. Screw on the canning lids and place the jars in a pot of boiling water for 10 minutes. Use enough water to cover the jars completely. Remove the jars from the water with tongs, and check to ensure that the lids have sucked down, an indication that the jars are fully sealed.
Change the type of ground, dried spices you use for your jam to give it a variety of flavor profiles. Grated or dried, ground ginger, cinnamon, cloves or even allspice can give strawberry rhubarb jam a warming taste that balances the sweet-sour taste of the jam.
Use different fruits in your strawberry rhubarb jam if you do not have enough strawberry or rhubarb. Options include peaches, berries — such as blueberries, blackberries or raspberries — or even cherries.
If you are substituting with other fruits, adjust the amount of some of the ingredients.
Use 1/2 to 3/4 teaspoons per cup of fruit, depending on how much pectin the fruits contain.
Sugar requirements are a 1/4 to 1/2 cup id sugar per cup of fruit.
Calcium water requirements are 1 teaspoon per cup of fruit.
One tablespoon of lemon juice per cup of low-acid fruit is needed.
Strawberry rhubarb jam will last a year in a cool, dark place. The jam will stay fresh for three weeks after the cans have been opened.
The recipe can be safely doubled to make more jam, or halved for a smaller quantity.