[mumofstig]

A jar of last year's pasta sauce, with the lid firmly screwed on - was decidedly off once I'd popped it to remove the lid  Still had a good vacuum, til it was opened.

Don't know what happened there 

Any thoughts?

[Annen]

could it have been contaminated by an old lid or jar?

[mumofstig]

It was a used lid - but I do sterilise them by boiling them before use, and the plastic lid lining is still intact.

I've thrown the jar out for recycling - otherwise it still looks good enough to use again 

[LotuSeed]

Late to the game but,
Did you use a one piece lid or a two piece one?
When I bottle I use the two piece lids (flat lid with rubber seal and metal ring)and it's recommended that after they've sat for 24 hours, the rings/bands be removed and the jars be stored without them. If a jar comes unsealed during storage it can be identified pretty easily. If, however, the rings are left on, it's possible for the contents to go off but the seal be kept intact (at least cosmetically) from the pressure of the ring. I assume the same is true for a one piece lid in that if it's tightly screwed on the thread will give the appearance of a seal simply by the pressure it puts on the rubber on the inside and not solely on the integrity of rubber to glass?? I don't re-use lids even if they've been sterilized unless it's for storing dry ingredients or storing something short term in the fridge.
 

[Chrysalis]

For a moment I thought this was a new game show for the TV - not Bake-off, but Pasta Sauce-off....

Mind you, it could be worse and end up P*****ed -off!  Sorry, Mods.  School starts this week and I need to begin to rein in my mania.......

MoS - I hope there's still some pasta sauce you can use

[mumofstig]

I use one piece lids with bumps in the middle that pop down under vacuum, I have always reused lids, and this is the first jar I've had that has gone off inside a sealed jar. That's what surprised me!

and yes, Chrysalis, there are now plenty of jars from this year's harvest