I love making homemade jam. I am not so fond of all the sugar required when using traditional pectin products. I have heard mixed reviews on the usual low-sugar pectin and getting the jam/jelly to set properly. Last year I started using Pomona Pectin, and I love it!
A typical recipe for blackberry jam requires 4 cups of mashed fruit and 7(!) cups of sugar. The recipe using Pomona Pectin also uses 4 cups of mashed fruit, but I only added 1 1/2 cups of sugar. The resulting jam tastes like the fruit rather than sugar. I did only get 4 1/2 cups of jam compared to the 8 cups that a traditional pectin recipe would yield. You have to consider the differnece in the amounts of sugar though.
I do prefer to can the low sugar jams in half pint jars. The jam will last 3 weeks in the refrigerator once it has been opened. A lower sugar content means less preservative so the jam needs to be eaten within 3 weeks. It is delicious so that is not a problem.
You can double, triple, halve, or even quarter a recipe with this pectin. The directions even include some guidelines for developing your own recipes. The new Preserving with Pomona's Pectin book is absolutely on my birthday wish list. You can purchase Pomona Pectin from the Pomona website.