Recipe from Fresh Preserving
I made this as a Christmas gift for some of my family. I really don't think you need sugar with strawberry jam, because the strawberries are typically sweet enough. Just make sure you use the pectin that you can use without sugar.
This is a canning recipe, so check out freshpreserving.com for canning tips if you've never done it before.
(This recipe made just a little over 5 8-ounce jars.)
4 c crushed strawberries (about 4 pints)
1 c no sugar added white grape juice
1.75 ou package No Sugar Needed Pectin
Red food coloring, optional
Prepare boiling water canner and sterilize jars and lids.
Combine strawberries and juice in a large saucepan. Gradually stir in pectin. Bring mixture to a full rolling boil (one that can not be stirred down), over high heat, stirring constantly.
Remove from heat and skim foam from top, if needed. Mix in food coloring if you would like a brighter color.
Ladle hot jam into hot jars, leaving 1/4" head space. Wipe rim and place lids and bands on jars to fingertip tight.
Process jars in boiling water bath for 10 minutes. Remove from water and let sit, undisturbed, for 12-24 hours. Lids should not flex up and down when center is touched.