Let’s imagine you had a jar of store brand strawberry preserves.
You opened it, consumed a quantity (on a tasty PBJ) and re-sealed the container.
You then store it in an air-conditioned but room temperature cubicle away from direct sunlight.
How long would the preserves last?
A day? 3 days? A week?
I’d think you’d get at least a week or two out of it before mold starts growing on it.
Er, anecdotally, that stuff will last for quite a while. I’ve never seen an opened jar of commercial preserves go moldy and we didn’t refrigerate them, though probably we ate it within a year. The sugar acts as a preservative. However, the authorities say 1 year unopened, 6 months opened and refrigerated.
If it went bad, you’d know it. Mold or dried out.
Could last quite a long time, if kept at “cellar” temps.
I will be making PBJ for lunch basically daily, so… I suspect this means I’ll experience zero spoilage.
The whole point of preserves is that they’re pretty stable, hence the name. When I grew up in Ireland it would never have occurred to us to refrigerate a jar of opened preserves, and they lasted at room temperature as long as they needed to - i.e. until the jar was finished, which might be weeks or months. Obviously they might spoil more quickly in a different climate.
If you found a long-forgotten jar at the back of the cupboard there might be mould on it. The received wisdom was that the mould tasted nasty, but was harmless. You could scrape off the mouldy top of the preserves and safely eat the rest.
Or thereabouts. All I’d add is that there are quite a few reduced calorie, or low sugar “preserves” made today. If the osmotic strength (ie sugar etc. concentration) isn’t high enough, they’ll need to be refrigerated.