Hi silver ether - Splenda is probably the best alternative for those who can't or won't have sugar (diabetics, carb-conscious, those with bowel and yeast problems, etc). Ultimately every food is questioned by some expert out there, but sugar, as natural as it is, isn't good for us either. So, in moderation I'm ok with it...
Ok, I've been reading, reading and reading....
For other preserving noobs out there:
Sugar is necessary in jam making because it is the ingredient that sets the pectin in the fruit (or added pectin). Basically, without sugar it just won't set. Additionally, sugar acts as a preservative, making the jam last a very long time, if properly sealed and stored of course.
So, the alternatives seem to be;
- using a different setting agent such as gelatin or a commercial no-sugar-needed pectin
- making a concoction that must be eaten sooner
- freezing
- long boil method, which reduces the fruit until really thick in effect resembling a jam
Which you choose depends upon your needs/wants and the fruit (some don't freeze well for example).
The thinking needs to be fruit spread, rather than jam.
The easiest thing that springs to mind at the moment is to begin with fruit that has a naturally high content of pectin. I did a search and found that apples, damsons, gooseberries, and redcurrants are among some of these fruits.
Also, sugar adds a LOT to the flavour, so using some sort of sweetening or flavouring ingredient would be best. Some ideas are: lime juice, lemon juice, apple juice, cinnamon, or a sweetener (spledna, etc). Keep in mind that sweeteners can ruin final taste and most don't do well with heat.
Hope that helps someone out there. I've learnt loads today.

Interests: land care, organic, permaculture, animal welfare, home education, tea.