Josh wrote in and wondered, “We just made some strawberry jam. Best jelly I've ever had. Do you know if you have to use such a huge amount of sugar? The basic recipe we used was adamant not to adjust or the jam would not set properly.”
Strawberries are very low in pectin so you do need to add a fair amount of sugar to get them to set. If you use less sugar they will not set. You can try using some strawberries that are not fully ripe and still have the white tips but I have had hit-or-miss success with this method.
One way to vary the amount of sugar, especially if you are not using pectin, is to mix the strawberries with a higher pectin fruit such as apples, blackberries, crab apples, cranberries, gooseberries, grapes, or citrus peel. This works for any low pectin fruit such as apricots, blueberries, peaches, pears, rhubarb, and raspberries.
If you are willing to use pectin you can use a commercial variety, and there are some low sugar ones out there, but another option is to make your own homemade pectin using apples or lemons. There are excellent directions in the book “Preserving Memories” by Judy Glattstein (who I confess is my mother and an excellent canner).
There are recipes that talk about using honey or other sweeteners but I find that most of them call for gelatin which I prefer not to use.
