Plums are abundant in August and early September. If you have a surplus, one way to store them is in plum jam. Any variety of plum can be used to make jam, or you can use a mixture of different varieties according to taste and availability. Dark purple plums tend to make a deeper coloured jam, whereas pink-hued plums like Victorias will make a lighter colour.
The quantity below will make about three or four medium-sized jars of jam. You can start eating it straight away, or it will keep indefinitely provided the seal of the jar isn’t broken.
2 lb (approx 1 kg) plums, any variety or a mixture
2 lb (approx 1 kg) sugar. I usually use granulated sugar
Wash the plums.
Halve and stone the plums. If the plums are large, chop the halved plums into pieces of the size you would like to find in the finished jam.
Put the chopped plums in a large saucepan with 2 Tblsp (approx 30 ml) water.
Cook over a very gentle heat until the juice starts to run. Then simmer for 15 – 20 minutes until the fruit is soft enough to mash with a wooden spoon. You don’t actually have to mash it, and I usually don’t because I like whole fruit jam, but it’s a good indicator for when the fruit is ready to go on to the next stage.
Add the sugar and stir until it has dissolved (a minute or so).
Add a small piece of butter. This is supposed to help stop the jam sticking.
Bring the jam to a full rolling boil – this means lots of bubbles across the whole surface of the liquid in the pan (see picture). Don’t lean over the pan and keep any children or pets out of the way. Boiling jam will sometimes spit, and as it is both hot and sticky it can give an unpleasant burn.
Boiling jam (All together now: "Double, double, toil and trouble....")
Boil until the setting point is reached. To test for setting point, scoop out a teaspoonful of jam and drip it onto a cold plate. It will form a pool. (If it forms a bead, your jam is ready – take it off the heat straight away and proceed to the next step). Wait for the pool to cool (30 seconds or so), then push it horizontally with your finger. If the surface wrinkles, the jam is ready. If the pool stays liquid, keep boiling for another 2 minutes and test again. I usually find this jam reaches setting point after about 15 minutes boiling.*
Remove the jam from the heat, and pour into clean glass jars. I find the easiest way to do this is to pour from the pan into a heatproof jug, then use the jug to fill the jars.
Seal the jars immediately. I seal jam jars with a layer of cling film and then a screw-top lid, but you can use any method of your choice as long as it is air-tight.
Let the jars cool, label them, and store in a cupboard until needed.
You can scale up the quantity as you see fit, but remember that you need plenty of space in the pan for the jam to boil without boiling over. If the pan is about half-full after you put the sugar in, that should be about right.
*I am told that a sugar thermometer makes it easier to recognise setting point. I’ve never used one, so can’t comment. The old-fashioned way works for me.