Jam trouble.....

[hamster]

Can anyone help me? Made loads of jam this year only to find some of it has
gone mouldy. Not all the jars have gone mouldy, just some but cant understand why?? I dont think Ive done anything different, strawberry, apricot, cherry and 1st batch of plum and damson havent gone mouldy. But the second batch of plum and damson have, the jars were washed and sterilised in the oven. Generally I use slightly less sugar 3/4lb per 1lb of fruit.

Also I put the lids on when the jars are cold, and noticed today that the jam seems slightly damp on the top, like a little pool of water, not sure why?? The
fill level is generally the same as the shop ones.

Last week in the cupboard at my mums found jam from 2 years ago sitting at
the back hiding opened it and it was fine dry and no problems, and advice would be greatly appreciated. When I boil for a set, I boil at a slightly lower temp for longer, to avoid burning because I use a large saucepan, will this
make any difference?? Was thinking of giving some as pressies, but not sure
now, what to do?? Thanks in advance...

[SarzWix]

The water is condensation, and it's happening because you're putting the lids on when the jam is still lukewarm rather than totally cold. I just put the lids on while it's still very hot, no problem with oven gloves on, and no condensation. This might be the cause of your jam going mouldy. I'd be tempted to up the sugar a bit too, you can add some lemon juice if it's a bit too sweet.

[Flummery]

You really need 1lb sugar to 1lb fruit to ensure the jam keeps. I seal up when hot too. Then during the day you can hear the anti-tamper tops click loudly as they depress when the whole thing cools and contracts.

[Alison]

I seal when hot also. Sometimes you do get jams going mouldy for what seems like no good reason but that tends to be after long storage. I'd be inclined to go with the comments above, up the sugar and seal when hot. Not sure of the implications of not taking to such a high temperature, I've always found this essential for setting, are you getting a proper set or are you simply reducing the water levels sufficiently to thicken?

[WrexTheDragon]

I agree with Flummery.

The sugar also preserves the jam and lids should go on hot to create the vacuum.

[Hans Mum]

Then during the day you can hear the anti-tamper tops click loudly as they depress when the whole thing cools and contracts.

i love that sound

[vicky]

I agree, seal when hot. Also check the lids are tight when cool, I had one batch where I didn't manage to put the lids on very tightly on the first attempt and some were loose - this batch was much more prone to mould...
And use more sugar - You can add lemon juice and zest if you find it too sweet.

[Pumpkin Becki]

They do say that reduced sugar/ diabetic jams don't have such a good shelf life as regular jam, but I assusmed that was only once the jar had been opened.

I still have some of my 2007 Damson jam which was 1kg sugar to 1kg fruit, jars sterilised in the oven and lids fitted immediately after filling to the brim, and its in perfect nick. If its not the reduced sugar causing problems, then I would put my money on cooling the jam before lidding.

Another thought - Did you use perfect fruit? Or was it damaged/ over-ripe? I understand you have to use perfect fruit for jams.

[Bren In Pots]

Then during the day you can hear the anti-tamper tops click loudly as they depress when the whole thing cools and contracts.

First time I made jam that click noise really made me jump, I couldn't work out where it was coming from at first.

[hamster]

Thanks everyone, was talking to my mum on Sunday, and we could only think that it was the lidding up thats done it. Incidentally this is the first year Ive had trouble.

So putting the lid on hot creates a vacuum and prevents the condensation, just read the the thread about the wax disks and stopping the air getting in, will that help?

Can I put the lids on as soon as Ive potted up? One more question, do I have to wait 15 mins before potting damson, plum or apricot where the fruit is broken up?

If I put 1lb sugar in how much lemon juice, does anyone know? (Two questions, sorry!!)

[WrexTheDragon]

I would always put the lids on ASAP after filling and wiping off any spillage. Wear gloves as the pots will be very HOT. You should always put a metal spoon in the jar when filling to prevent the jar from breaking.

I don't use wax disks, but they do no harm and extra protection. You do no see any of the major jam manufacturers using them do you!

I would also add one lemon and a pound of sugar.

[Pumpkin Becki]

The WI show judges always say that you either use a screw cap, or a wax disk and cellophane top. Never mix the two (apparently, I don't know why, but I know you get marked down in a competition, so I guess there must be a real reason behind it).

[Madasafish]

I like mould on my jam. It tastes OK...Puts hairs on ones chest (allegedly).

Always get it as I use far less sugar than most recipes- about half... All in the cause of healthy eating. Too much sugar ruins the taste imo.

[Hilary B]

You CAN make jam with less 'sugar to fruit', but you simply boil away more water and end up with less jam (but a more intense flavour). With poor-setting fruit you can PLAN on this approach, and improve the set (a bit). It needs to have a certain level of sugar per jar, but some of that will come from the fruit. A really accurate thermometer, used in exactly the right way (which very few of us actually manage) does measure the sugar content of the finished (still boiling) jam. The sugar content is what causes it to boil at more than 100 degrees C. The various setting tests also work.
Jars need sealing either immediately (and fruit may 'float') or not until REALLY COLD (not just cooled from hot).
Even so the occasional one will get a mould 'skin', usually because we are all human and sometimes things don't go to plan. I like the wax discs, because if it DOES get mould on, you can lift of the disc, complete with mould, and the jam underneath will be fine (but maybe not for anyone allergic to penicillin, or you can reboil after removing the mould).

[LilyRose]

While we're on the subject. . . .
I've got my batches of jam/chutney all jarred up and away, but I want to re-pot some. Was thinking that if I sterilize the new jars, chutney would be ok to just transfer? Probably have to re-heat the jam though - warm enough to re-pot or boil it up again? what do grapes with experience of these matters think?! :s