Apricot Jam: Crack the Stones for the Best Part

Three stages

1. Prep — halve, crack ten stones, keep the kernels

   Halve the apricots along the suture and twist the halves apart; the stone usually comes free with a fingernail. Cut each half into quarters — apricot flesh collapses fast, and pieces larger than a quarter of a fruit will vanish into paste before the jam reaches temperature.

   Crack ten stones with a hammer on a hard surface, pick the kernels out and tie them into a small muslin bag. The bag goes into the pan with the fruit and comes out before potting. Do not use more than fifteen kernels: the same benzaldehyde that gives the aroma also contains traces of hydrocyanic acid, and ten is the amount used in every European apricot jam recipe for a reason.

2. Cook — the kernel bag goes in, the foam comes off

   Combine the fruit, lemon juice and kernel bag in the pan and bring them to a simmer for 5 minutes, which starts the juice running and gives the kernels time to infuse. Then add the sugar and stir until dissolved, off the heat, before bringing it to a hard boil.

   Apricot throws a thick, pale foam for the first eight minutes; skim it into a cup rather than stirring it back, because it is mostly air and it will leave a scum line in every jar. Boil to 104 °C, add the pectin blend, and hold at 105 °C for 60 seconds. Fish the kernel bag out with a slotted spoon and squeeze it against the pan — that squeeze is where the last of the almond aroma lives.

3. Seal — 10 minutes, and keep the jars dark

   Fill warm 250 ml jars at 90 °C with a 6 mm headspace and process for 10 minutes in a boiling water bath. Apricot jam is dense with suspended fruit and traps air against the glass, so run a thin spatula down the inside of each jar before capping.

   Store in the dark. Apricot colour comes from carotenoids, which are more heat-stable than the anthocyanins in berries but more light-sensitive than people expect — a jar on a shelf fades from deep orange to amber by the end of the first year.

Failure diagnosis

Four things go wrong with this preserve more often than anything else. Open the one you are looking at.

• Will not set

  Apricot pectin varies wildly by variety and ripeness, which is why this recipe carries insurance. If the plate test shows syrup, add 1 tsp more pectin in hot water, boil 60 seconds at 105 °C, and stop — apricot turns to leather if boiled past 108 °C.

• Graining and crystals

  Medium risk: 800 g of sugar against only 2 tbsp of lemon juice is a fine margin. If you have ever seen a sandy crust on apricot jam, it was a batch boiled a few degrees too far; pull yours at 105 °C and no higher.

• Mould or spoilage

  The kernel bag is the usual culprit: if it tears, whole kernels sit in the jam and stay below 60 Brix inside. Tie it with a double knot and check it before the sugar goes in.

• Colour loss

  Apricot goes amber rather than brown, and slowly — about 15 percent of the colour in a year. This is the most colour-stable jam in the collection and the one to make in quantity if you dislike waste.

On the same shelf

Other stone fruit recipes, all already published.