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I made plum jam a few weeks ago which tasted lovely...however, when i opened a jar after it was cold it was really hard and very hard to spread.

Dead disappointed as i love plum jam.  I know where i went wrong as i couldn't get it to the  setting point  and 'Delia' suggests putting lemon juice in which i did...i shan't bother next time.

Anyway is there any way to correct this as it still tastes lovely but you have to have a slice rather than spreading it!

when you say cold do you mean its been in the 'fridge, cos room temperature should help make is less solid

maybe melt and cool small portions at a time

can you say why lemon juice would make it so hard

I've had the same problem, perhaps from overcooking ?, ended up melting it in the microwave a bit at a time, lovely on ice cream, also put it in the bottom of the bowl with a sponge on top, that seems to work

Mum makes fab jamevery year, but sometimes the consistency is a bit hit and miss.  For too thick jam, we just add a teaspoon of boiling water to teh top & stir furiously with a knife until it eases off.

Job done, jam gone.

Quote from: kippers garden on October 18, 2006, 16:50:11
you have to have a slice rather than spreading it!

Some of my mum's jam and marmalade was always sliceable, either due to long keeping or pectin-rich fruit. We ate it in slices with cheese after dinner. She told us it was a Portuguese delicacy, so we felt dead sophisticated and thought she'd done it on purpose. We didn't quite fight over it, but nearly ::)

You gotta hand it to my mum 8) ;D

might it not be the amount of sugar used that contributes to 'sliceable jam'  :-\

Plum has a high pectin content, so does not need any extra like you get in special sugars.  Did you cook the plums beforehand in a little water before adding the sugar.

Boiling it for too long will make the jam harder too and, AFAIK, is impossible to rectify because of the sugars.

Best bet is to slice it, shove a jar-full in the food processor and blitz before re-jarring it - one open jar at a time as the sterility will be destroyed. Warm it before use, tsp by tsp. All of which is a bit of a palaver. With cheese is a fantastic idea provided it's not too sweet.

To me the obvious use has to be jam tarts!    8)
Optionally served with icecream of course  ;D


In terms of addressing the problem for future though, how are you measuring setting point? 
I know that a lot of books use sugar thermometers and such, but personally I just don't think that is measuring anything directly related to setting - MUCH better to just use the old fashioned method: 5mins rolling boil (or whatever recipe estimates) then cool a teaspoonfull on a cold saucer every minute or so until it's got the set which you like.

Call me a luddite, but you're stood watching it anway and it's less trouble than washing a termometer!

Other than that, Grant could be right, though - "Jam sugar" as sold has added pectin in it which I don't think you should need for plums.

Strange, this - some recipes call for Lemon Juice AND Pectin!!

Hi thanks everyone.

I didn't use a thermometer i used a cold side plate (from out the freezer) to check for setting point and i boiled the plums in a little water b4 adding the sugar etc

Anyway jam tarts is a fab idea, so too is the jam sponge and ice cream idea..thanks

Jam setting depends on a number of factors, including the level of pectin in the fruit, the level of acidity present, and the level of water within the fruit. In a hot dry summer like the one we've just had, some fruit will be denser, and the level of pectin will be a lot higher for the weight of the fruit.
Pectin is released from the flesh of fruit by boiling it in the presence of acid, so if the fruit is naturally acidic, this will help release the pectin. You can test for the existing level, and so avoid spending money on special sugars. You do this by boiling the fruit (some will require a little water) for at least 10 minutes, without any sugar added. Take a teaspoonful of the fruit juice and put it into a small container (I use an old egg cup). Let it cool. (Remove the pan of fruit from the heat while this little bit of juice is cooling.) Well away from the cooking area, drip a couple of teaspoonfuls of methylated spirits into the fruit juice in the egg cup. Wait a few seconds. If pectin is present, when you tip out the contents of the egg cup onto a plate, you will see a distinct jellified blob, with the meths as a separate lquid. If the blob isn't a blob, is broken up and more or less liquid, then there isn't a high enough concentration of pectin to set the jam. This can be remedied by boiling the juice further, and/or by adding something acidic like lemon juice, or by using pectin or adding juice rich in pectin. You can re-test the juice any number of times until you get the result you want. The key is to do all this before you add the sugar.
Modified to add: boiling past "jam" setting point on the thermometer causes the nature of the sugar to change.

Quote from: calendula on October 18, 2006, 17:27:02
can you say why lemon juice would make it so hard

The extra acid in the lemon juice will extract more pectin and help it set harder.

I'll try the lemon trick on my bit too runny blackberry jam.

I've made about 5 separate batches and only one has been 'solid'.

thanks to all for the tips.