THE FIRST BOIL
If you’ve ever bitten on grapefruit or seville orange peel, you’ll know how intensely bitter it is. The first boil in this process removes that excess bitterness. It also extracts pectin from the fruit and then concentrates it as the water reduces.
Pectin is naturally found in the cell walls of plants and fruits, and has been used as a thickening agent for centuries. A high concentration of it is found in the piths and pips of citrus fruits, which is why it’s traditional to boil the pips wrapped in muslin, before squeezing out as much of the pectin as possible.
The sugar draws the water away from the pectin, forcing the pectin strands to begin to knit together. After a rapid boil the sugar thickens and the pectin reforms into a gel consistency.
Once fruit has been turned into marmalade and put into a jar, it will keep, sealed, for up to six months. However, this is only the case if the jars are completely sterile. If any bacteria gets into the jar, it will shorten the marmalade’s lifespan considerably. To sterilise the jars, wash them thoroughly in hot, soapy water, rinse well, then put in an oven at 120C/fan 100C/gas Ω for 10-15 minutes until piping hot.