I don't use sugar substitute but I can tell you that I *never* add all the sugar called for in marmalade and jam/jelly recipes...they are just too sweet for my palate. I use about 1/2 to 3/4 of the sugar called for and I have never had issues with my jams. If I'm using a low pectin fruit, I will just use the pectin for low sugar jams...

Thanks. This one doesn't use pectin, and the oranges are sour, so a good bit of sugar is needed, but that seems like too much. I still have some from last year and it tastes great, but I could do with less sugar! The recipe calls for a water bath, so I guess it would be okay.

a good tip: if you keep the seeds and tie them up in a cheese cloth, you can throw them in with the marmalade while it's cooking down and it will help as well. Seeds have a lot of pectin in them.

Since I don't use as much sugar, I generally have to cook my marmalade/jams down for a long time...it's definitely not something that you want to do if you are in a rush or starting a marmalade late in the day. LOL. I learned this the hard way.