A softly set fragrant marmalade made with the best of the season's citrus fruit. Sift out the peel when you're done if you prefer it shredless. With the peel, yield 1.5litres, without about 750ml.
Start by weighing the blood oranges and note down the weight (about 600-650g usually). Wash them under hot wash well, scrubbing to get any wax coating off. Also, sterilise your jars (see notes).
Cut the blood oranges in quarters and slice them as thinly as you can possibly manage - use a mandolin if you are careful (and brave enough!) or the sharpest knife you have. Discard pips.
Scoop the sliced fruit into the Inner Pot with all their juice plus that of the lemon. Add 250ml water and close the lid, setting to 12 minutes Manual (High). Allow a NPR. Cancel the Keep Warm function
Weigh out 1.5 x the weight of the oranges in caster sugar (you can go as low as 1.2 if you prefer it less sweet) and add to the cooked fruit, stirring to help it dissolve.
Press Sauté and stirring constantly to avoid catching and burning on the bottom of the pot, heat until an instant read thermometer shows 104.5˚C. Take off the heat and allow to cool briefly whilst you retrieve your sterile jars from the oven/dishwasher (see notes).
If wishing to make shredless marmalade, simply pass it through a fine meshed sieve, pressing firmly to ensure as much pulp goes through just leaving the peel behind. Scrape the jelly off the underside of the sieve. Ladle into the hot sterile jars, sealing the lids immediately. If leaving the peel in, then simply ladle into jars, trying to distribute the peel evenly between them.
To sterilise the glass jars, either wash in hot soapy water then place in the oven on low (about 100-120˚C) until dry, which may be 20-30 minutes. OR put through the hottest cycle on the dishwasher.
Whichever method you use, do not touch the insides of the jars with your fingers to prevent contamination and make sure you use the jars whilst still warm. Which means you'll probably need to start sterilising them an hour before you start making the marmalade as it is so fast in the Instant Pot!
Once open, store in the fridge. Unopened jars will keep for many months in a cool dark cupboard.