It mentions a more careful cooking technique to avoid using pectin which when used seems to necessitate more sugar. It is 50:50 fruit and sugar so more sugar wouldn't be a good thing, in my book. Other recipes suggest putting spoons in freezer to be ready when doing the consistency test. I like this recipe as it assumes you'll want to store your jam on the shelf so gives canning directions. It also directs to pre-warm the sugar which is new to me...
We've been on a smoothie kick so have been intentionally freezing the discounted fruit I find on sale. Unfortunately, buying things at the discounter means clam shells. If the discounter didn't sell it, the produce would wind up in the landfill, clam shells and all most likely.
I would probably put the cooked fruit through a sieve as I don't like too many small seeds in my jam (would that be jelly, then?), but to each their own. Sounds like a fun winter project. When I made orange marmalade it was easily an hour standing at the stove stirring the steaming pot but I got a great facial out of it, too!
PS I don't recommend homemade marmalade too much as it used only a small amount of fruit...Anyone have a better way to use up excess citrus (juicing or making sorbet?)?