Last week I made Delia's Dark Chunky Marmalade, using Seville oranges that had been frozen for several months (I therefore used 1.7kg fruit instead of 1.35kg). I have used this recipe before and it worked perfectly, cooking in stage 2 taking around 3
But this time the setting temperature of 105˚C was reached within 10 minutes of reaching a gentle simmer (checked with 2 thermometers). I continued cooking for 2.5 hours more. The result is delicious, but only just usable because of its consistency.
Why do you suppose my marmalde reached the setting temperature so very quickly?