How much stevia do you use to replace a cup of sugar?

Oh this is my ball of wax. I’m with you, no commercial pectin is needed. But pectin is needed to make jams and jellies set. Like you said, it exists in most fruit but in varying amounts - strawberries hardly any; gooseberries tons. So knowing which fruit you are starting with is important. And if you want to cut down the sugar, adding pectin helps with the gel since sugar is part of the reason it does gel.

I have found that I can use three pounds of fruit with 2 cups of sugar (more or less) and get a good gel if I use home-made apple pectin. It is like pumping up the pectin level of fruits that have very little and thereby making it more likely to set.

Of course cooking time and acid level of fruit plays a part too. And while not many folks want to get that complicated about it (I admit I am a freak) I have noticed a distinct difference in setting time and texture and sugar requirement between the different fruits I use. You just have to stare at currants for them to set up while strawberries are more fickle.

Commercial pectin depends on gobs of sugar (generally) while low-sugar pectins lend an odd structure to jam. But making your own pectin is easy and a good way to use all the crab apples around Portland. I know not that many folks care to go this route since it is a lot more time consuming in the beginning. But you need make it only once a year and can it up for future use.

The general rule of thumb for use is 4 cups fruit (sliced or mashed) or juice, 2 cups sugar and 3/4 apple pectin. Some fruit needs the acid (you can tell by how tart they are) and some do not. Peaches appreciate it. Generally I can get that to cook up in 15 - 20 minutes in a wide pan over high heat. Of course the greater the quantity and the larger and taller sided the pot, the more time it will take. The above recipe will make at least 4 to 6 half pints depending on how firm you like it.

So that is just another thought but the real point to all of this is that, like you, I make jam outside the box. Also, once you get out of the habit of using commercial pectin you do not have to worry about the magic PH bru-ha-ha those products require for set. It becomes a much more intuitive process that most cooks are familiar with -- sight and smell.

I use 4 1-gram packets of Sweet Leaf stevia to replace one cup of sugar. I have not experimented with other types of stevia. I suspect (although I haven’t tried this yet) that one could successfully replace up to two cups of sugar in a jam recipe with stevia.
I would be hesitant to replace all of the sugar with stevia because I’m not sure that the jam would set up properly, and I don’t know if it would be safe to can without ANY sugar.
I find that replacing one cup of sugar with stevia produces a fruit jam that tastes no different from all-sugar jam and reduces the calorie count by nearly 800 calories per batch.

Have you tried Pomona pectin? If you don’t like the taste of jams made with regular pectin, you may not like it. But it really great. It uses calcium to gel instead of sugar so you can add as little (or no) sugar as you like or non-sugar sweeteners like stevia or honey and it will gel everytime. I love it.

I’ve been using Harriet’s principles completely without sugar, and with very little honey or other sweetener (rapadura has been the other one i’ve used frequently). I made a variation on her apple pectin with currants -- essentially, just currant juice that I make by simmering currants in water for 20 minutes or so then straining them -- which has the nice benefit of adding acidity so you don’t really have to add lemon juice. so I make peach-currant, blackberry-currant, strawberry-currant jam with about 1/2 cup of honey for 2 pints of jam.

letting go of the pectin, for me, means I throw out the cookbook and only use it as a guide for how to prepare the fruit (should I crush the blackberries? strain out the seeds? how fine should I chop the peaches?) and then get creative with combinations of herbs, fruits, and sweetener. I’ve also enjoyed sampling different batches of honey to find one with a mild enough taste to let the fruit shine through -- and also found that, a month or two later, my jams made with strong-flavored honey have a truly unique quality that’s wonderful and surprising.

Thank you all for your insight on a more natural approach to jams. I really like the taste of the fruit and the added sugar is really too much for me.