Your fresh jam will keep in the refrigerator for a few weeks or in the freezer for up to year. You can get a package of pectin at your local grocery for a buck and some change. The package looks like this -
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There is also a No-sugar needed pectin that would be fun to try if you like your jam to taste more like fruit and less like fruit flavored sugar.
Recipe For "Lemon Berry Mix-Up Freezer Jam"
Ingredients:
1 pouch Ball® Fruit Jell® Freezer Jam Pectin
1 1/2 cups sugar
4 cups crushed berries (strawberries, raspberries, blackberries and or blueberries)
Zest of 1 large lemon
Crush berries with a potato masher. Measure 4 cups crushed berries; set aside. Combine freezer jam pectin and sugar in a medium bowl, stirring to evenly blend. Add crushed berries and lemon zest. Stir for 3 minutes. Serve immediately, if desired. For longer storage, ladle jam into clean freezer jars, leaving 1/2-inch headspace; apply lids. Let stand until thickened, about 30 minutes. Refrigerate up to 3 weeks or freeze up to 1 year.
I found this recipe at Homecanning.com.
Pectin is a naturally occurring substance found in fruit.