I’m posting this here as the site I tried to post it on decided not to accept the input after I spent ages typing it.  The post was in response to someone asking how to make jam from Josterberry.

Jam? I make josterberry into jam just like black-currant. Lots of acidity in the fruit so no need to add pectins.

1lb berries
1/2 pint water
1 to 1 1/4 lb sugar

Jam pan or biggest saucepan you can find.
Wooden spoon
Jars, with clean original or fitting lids if you can find them.
Ladle
Jam funnel if you have it.
A sideplate or saucer.
Wax discs to fit your jars.

Berries – ideally take off the stalks and flower residue but I find if you simmer the fruit long enough they soften sufficiently that it doesn’t matter. TO your taste, its you that has to do it!

See how sharp they are. For blackcurrants, I’d use the full 1.25lbs sugar. For under-ripe gooseberries the same. For ripe gooseberries, only 1lb of sugar. Your tastebuds will tell you which end of the blackcurrant <-> ripe gooseberry scale your fruits are on. This would probably encourage me to make a small batch rather than scaling the above figures up! (Which is, otherwise, easy enough to do – i can fit about 4lbs of fruit in my jam pan!)

Prepare:

The above quantities are going to make about 2 to 2.5 lbs of jam. Get enough jars ready, cleaned out, then put them in the sink and pour BOILING water in from the kettle. leave then to stand. If you have the original lids, treat them the same. Whilst you’re sterilising, do the funnel and ladle.

Method:

Put the fruit and water in a big pan. Simmer *slowly* – I mean heat it until it *just* starts to boil then back it off a notch so you have bubbles JUST rising but not boiling hard. Let it simmer until the fruit is all soft. They’ll burst – if you like jam with big chunks of fruit in, then these are not the fruit! 🙂

Once the fruit is all softened, pour in the sugar. Still on a low heat, mix it well to make sure the sugar is all wet, surprising now long a “Pocket” of dry sugar can hold out against the juice… and then until it’s all dissolved, which you can test by putting your big wooden spoon in and seeing if you can hear any sugar grating against the bottom.

Once the sugar is dissolved, crank up the heat until you have a good rolling boil. WATCH it as big bubbles can form in the sugary juice which can lead to overflow! Just blow across the top of the pan if it threatens to boil over.

If you have a thermometer that;’s accurate between 100 and 110 c fine, but I find it very hard to get a consistent reading. You’re actually aiming for 104 degrees. As the excess water boils off the temperature will gradually rise. The “traditional” test is still easier I find. After a few minutes (and this process typically only takes five to ten minutes) dip a spoon in the mix, allow almost all the jam to drip back off into the pan, then catch the last couple of drips as a small “dot” on the cold saucer or plate. Set the plate on an angle so the drip doesn’t run. Give it 30 seconds, then hold the plate so you can see light shining off the surface of the drop, and push at the side of the drop with your thumbnail. If it remains a liquid, it’s not done yet. When you can see a ‘skin’ start to form, which will wrinkle up when you push at it, you’ve reached the point when the jam should set. Don’t go too far! If you boil it too long, you get less jam, the flavours start to disappear, and you CAN go past the point where it will set to the point where you’ve made compote instead of jam! 🙂

Once you reach a setting point, take the pan off the heat, and allow it to sit for five to ten minutes. Whilst it’s sitting, tip the sterilising water out of the jars, allow them to drain dry (don’t use a tea-towel unless its fresh and clean, you’ll be introducing unsterileness!) and set them with the funnel near the pan.

Allowing the jam to sit before you jar up stops the remaining solids from floating at the top of the jelly when it sets. Give the pan a quick stir when you start to jar up.

Ladle the jam into the jar, stopping when the jam is just above the “shoulder”.

EITHER put the wax discs on the surface of the jam at once, or wait for it to completely cool. It will take some hours to completely cool, so just let it stand. Don’t panic that it may not have set, it’s still warm! Overnight is best.

Once it’s completely cool, add the discs if you didn’t already, and then screw on the tops as firmly as you can. Label up, store. You’ll probably have a part-filled jar, so that’s your breakfast toast sorted!! 🙂

NOTE that the basic recipe varies a little depending on the fruit, in particular on the acidity. If you make jam from strawberries, apricots, etc., you need to add pectins, which is most easily done by getting a bottle of “Certo” – supermarkets tend to stock this next to the sugar. But blackcurrants don’t need it.

I hardly ever buy jam or marmalade. It’s so easy to make, the flavours are so much better when you make your own, and I love the row of colourful jars on the shelf! Here’s a pick from a summer or two back – blackcurrant on the left, strawberry and tayberry on the right, redcurrant at the back https://www.flickr.com/photos/ccomley/5914346569/