Jamming is preserving fruit in sugar. Jam is fruit cooked in sugar. There isn’t anything fresh, low-calorie or low-carb about jam, let alone keto or other paleo-nonsense. We eat jam because it’s sweet, not because it has massive nutritional value – it doesn’t.
So don’t believe the labels saying ‘no sugar added’ or ‘low sugar content’. Such jam will either have horrifying chemicals in it or honey, maple syrup or concentrated fruit juice, which – you guessed – contain sugars.
Fruit and sugar in more or less equal ratio – that’s jam. You can add some enhancements, see below, and less sugar to fruit high in pectins: pears, apples, quinces, gooseberries; i.e. the less delicious jamming labels. Cook it down more or less, depending if you prefer your jam runnier or harder. If you sit the fruit in sugar and then let it dissolve slowly, it will firm up the fruit chunks; if you rapidly bring the lot to the boil, it’ll be mushy and spready.
I’d thought I’d be smart – and add way less sugar than the universally prescribed, roughly equal amount. Not so smart – unless you like your jam dripping off your scone in watery trickles. The exercise ended in re-boiling and re-potting the lot so, though delicious end product, it was major hassle.
So perhaps like with meringues, candy floss, toffee and caramel sauce – if you don’t want sugar, don’t eat jam.