Space Jam II
November 17, 2013 12:07 PM   Subscribe

My jam did the thing again -- it levitated in the jar overnight. I took a photo this time. I'm asking again in the hopes that someone new may have a definitive answer, as I'd like to know for sure if this means the jam is now inedible.

-- As you can see in the photo, the jam has floated up in the jar, leaving a clean space underneath. I assure you, it was NOT stored upside down (neither by me nor by any mysterious trickster secretly living in my crisper). You can see that there is also free space under the lid, which would not be the case if it had been upside down.

-- The bottom of the jam is quite straight and even.

-- Last time, it was about two weeks in between uses. This time, I used (or tried to use) the jam two days in a row, so I know the levitation definitely happened within 24 hours of last use.

-- The jam is not expired. I probably opened it two weeks ago; the label says to use within 20 days.

-- It's always kept in the fridge. My fridge has not been acting up and all other foods inside are obeying gravity.

-- In case it matters, it's pomegranate. Last time, it was apricot.

I'd just like to know, for sure, what this is (best guess is bacterial outgassing, but it's still just a guess) and whether it's dangerous. Thanks.
posted by (alice) to Food & Drink (34 answers total) 14 users marked this as a favorite
So.. I've had this happen plenty of times with jam I make, and it happens while the jars are still sealed so in my case it wouldn't be outgassing. I've always assumed the fruit part is less dense then the jelled liquid part this the fruit moves to the top.
I've had it happen with both strawberry, and peach jam and eaten it with zero ill effects. Hell I have Peach jam (still sealed) from 2 years ago that is fine to eat.
posted by edgeways at 12:37 PM on November 17, 2013

My guess would be that you sealed the jar while it was full of warm air, and then as it cooled in the fridge, the air at the top contracted, pulling the jam up. I would happily still eat jam in that state, as I doubt it has much to do with the jam itself. But I'm by no means and expert, and may be wrong about what happened.
posted by duien at 12:50 PM on November 17, 2013 [3 favorites]

Response by poster: Sorry, one more detail: the bottom of the jar was definitely filled with air/gas, not clear liquid. I poked a chopstick in there to check; after I pulled it out, the jam made a sucking noise and fell back down in the jar.
posted by (alice) at 12:50 PM on November 17, 2013

oh huh.. sure enough. I can't think of a reason for that which doesn't involve someone fucking with you.

are the lids really bowed when this happens?
posted by edgeways at 1:00 PM on November 17, 2013

Here's my guess: This particular glass jar is very very slightly narrower at the bottom than at the top, and this is what levitated the jam.

In the beginning, they used a hot process to can the jam. The jam stuck to the glass as it cooled and remained that way because it was not jostled too much during transit (because hey it's a glass jar full of sticky stuff). Also the weight of the jelly and the amount of it against the glass kept the whole blob in place. As you used up some of the jam, and poked at it with utensil while turning the jar this way and that with your warm hand, you loosened the jam from the sides as well as reduced the mass of the blob. Finally, the glass is much cooler now than at the start when the jam went in, so the glass has shrunk enough for the jam to be squeezed relative to where it began (in a hot jar). The slight squeezing force was just enough to counteract the weight of the jam and the friction against the glass, and the blob of very jellyish jam levitated. (I suspect this would not happen with softer, more paste-like sticky jams.)

Alternatively: Fridge Faeries.
posted by zennie at 1:18 PM on November 17, 2013 [2 favorites]

I don't suppose you have a caliper? :)
posted by zennie at 1:20 PM on November 17, 2013

after I pulled it out, the jam made a sucking noise and fell back down in the jar.

This would appear to confirm duien's hypothesis. Something is creating a vacuum in the top of the jar and sucking the jam upwards, leaving a void in the bottom of the jar. When you poke it, air rushes in, hence the sucking noise. But... the jam should have gone down immediately when you opened it, so... nevermind....
posted by klanawa at 1:58 PM on November 17, 2013

I like zennie's theory. duien's "contracting air at the top" theory was my first thought, but consider: why would some of the contracting air somehow move around to the bottom of the jam? If there was no gas down there to start with, where else would it have come from? Unless of course it's gaseous bacterial waste, which still seems like a possibility.

It would help to know if there was a lot of positive pressure inside the jar. Was the lid bulging and inflated? Was there a hiss of escaping air when you unsealed it?
posted by contraption at 2:21 PM on November 17, 2013

If the total volume of gas were being reduced or increased, that'd be pretty obvious when you opened the lid. Seems to me the air already present in the jar is being redistributed. As to how - the only way I can think of is the combination of the jam in the jar and the vibrations of your refrigerator are creating an improptu pump. Anything exotic about the refrigerator, its vibrations, age, or the placement of your jam jars therein?
posted by labberdasher at 2:27 PM on November 17, 2013

Response by poster: To answer your questions: the lid was normal, not bulging. No hiss when I opened the jar. Nothing weird about the fridge, which is probably 5-6 years old -- I would mention anything I thought was unusual. It's also beside another jar of jam that's not floating.

I took another look at it just now (it's been in the fridge) and another air pocket was already forming -- maybe 2mm or so of space.

Last time I asked, someone pointed to a BoingBoing user that had the same experience with Raspberry Smuckers. That's another photo, for reference.

Nice hypothesis, Zennie -- but no caliper, sorry!
posted by (alice) at 3:00 PM on November 17, 2013

Is the blob of jam just contracting in the fridge, maybe?
The boingboing blurb mentions that when it returns to room temp it starts to return to normal, then climbs up again when it gets cold.

As to why it contracts upward, I'm not sure. I think it could have something to do with disturbing the jam at the top maybe pressing it outward, causing it to stick to the glass better at the top. Or something. Some way the jars are treated at the factory might introduce a layer of, I dunno, something, between the jam and the glass, and that gets disturbed when you spoon/knife out some at the top, and less so further down in the jar?

Try stirring the jam with a knife, all the way to the bottom, and see if it still happens?
posted by Mister Moofoo at 3:42 PM on November 17, 2013 [2 favorites]

That photo from BoingBoing blows zennie's theory, as far as I'm concerned. It shows the jam forced all the way up against the lid despite the fact that the top section of the jar tapers sharply inward for a good inch before that. If the jelled contents were exerting outward pressure that wedged them upward, you'd expect them to stop once they hit the point where the jar begins to narrow.
posted by contraption at 3:42 PM on November 17, 2013

I don't know but maybe something here might lend a clue -- My Wine Won't Stop Crying — A Mystery In A Wineglass. Essentially surface tension + ??? component of jam = levitating jam!
posted by amanda at 3:52 PM on November 17, 2013

If AskMe doesn't turn up a definite answer (or even if it does), maybe consider sending the jam company a letter? Odds are good that they've heard of this before and some engineer responsible for the bottles knows what's up. Whether that answer makes it down to the customer service people is another matter, but I'd be curious to know what they say.
posted by zachlipton at 4:07 PM on November 17, 2013 [1 favorite]

For what its worth, yes I'd eat it. I too have occasionally had jam do this; I have no idea why it does it, but its always been fine afterwards. (I like to imagine it's now fat-free: all the calories fell out.....)
posted by easily confused at 4:09 PM on November 17, 2013 [1 favorite]

I wouldn't eat it; i'd be afraid that it had botulism, like how a dented can is a sign of botulsim. The jar can't bulge outwards, so perhaps the jam is bulging upwards instead.
posted by windykites at 5:06 PM on November 17, 2013

This would make sense to me if the jam were made and canned in low oxygen conditions-- which would be ideal for keeping the best (non-oxidized) flavor-- so that if you opened it up and used some, then closed it up again, it could absorb the 20% of the included air after closing which would have been oxygen, and that would have produced a significant vacuum at the top.

But that wouldn't have sucked it up significantly by itself because there was no air space in the bottom. The space down there had to have been filled with gas from the body of the jam.

But that in turn would be possible if they cooked the jam not under nitrogen, which would be one way of excluding oxygen, but under carbon dioxide, which would have been highly soluble in the jam itself; in that case, the vacuum produced by absorbing oxygen at the top could have caused dissolved carbon dioxide to come out at the bottom.
posted by jamjam at 5:16 PM on November 17, 2013 [1 favorite]

Actually, enough dissolved carbon dioxide would explain this without reference to absorbed oxygen.
posted by jamjam at 5:20 PM on November 17, 2013

I like the dissolved gases/gases produced by bacterial production or something else inside the jar theories.

Bit of a left field theory: dissolved ethylene? Using fruit that's a bit overripe might ramp up ethylene production, so does "wounding" plants (like the fruit being chopped/crushed small before cooking to make the cooking go faster) and heating them (IIRC there is a slightly inefficient way of producing ethylene commercially by heating plant matter). Would ethylene readily dissolve in jam when sealed and come out when unsealed?

Also, the fruits used in the OP's two jars and the boingboing link (apricot, pomegranate, raspberry) are all low pectin fruit. If these jams used typical commercial dry or liquid pectin this probably wouldn't mean anything, but if they used something like a ground-up apple pomace (possibly readily available in the same production space) to make the ingredients list more "natural", that could be an ethylene powerhouse - apples already are, and "wounding" them by juicing (this is where you get pomace) and then adding heat could add to that.

I mean, kind of a Rube Goldberg way of explaining a dissolved gas in the jam, but not too far out there.
posted by jason_steakums at 8:13 PM on November 17, 2013

Was the brand of jam the same type both times? Same size/shape jar?
posted by Conrad Cornelius o'Donald o'Dell at 8:16 PM on November 17, 2013

I would contact Smuckers or the jam company and ask. If anyone knows the answer, it's them. And I'd bet they've been asked this. I think companies still keep 1-800 numbers on their products, which I've never understood. If not, I'm sure their website has contact details. Report back if you talk to them!
posted by AppleTurnover at 8:40 PM on November 17, 2013

Response by poster: Don't mean to threadsit but I did contact two companies last time (including Smuckers). Was somewhat rudely dismissed by one, ignored by the other. I can't quite remember what brand the first jar was but the shape was roughly the same.

Thanks for all the input so far!
posted by (alice) at 8:57 PM on November 17, 2013

Have you tried putting the jam in a different refrigerator, or keeping it cool in an icebox? Or putting the same jam in a different jar?
... I mean, this question is reminiscent of the best articles in Scientific American back in its heyday :)
posted by labberdasher at 9:07 PM on November 17, 2013

Oh hey does your fridge have really good seals? Maybe the pressure difference when opening the door sucks some air out through the lid, since those flimsy metal jam jar lids aren't great at staying really sealed once unsealed. If there's some jam residue between the lid and the glass that could seal it pretty well except when there's a pressure difference big enough to break the seal. So the fridge is opened and the burst of low pressure outside the jar sucks air right out of the top space in the jar until the difference is low enough that the seal holds again, but it's still a bit low so the jam slowly advances up into that low pressure space. Then there will be low pressure underneath the levitating jam, which could maybe pull a bit of dissolved gas out of the jam to create a little bubble for the jam to rest on while it clings to the sides of the jar. And the cycle repeats every time the door's opened.

Plus the flimsy metal heat-conductive lid cooling the air and top of the jam and the glass jar insulating the rest of the jam might make for a bit of pressure difference when cooling down after use.
posted by jason_steakums at 9:55 PM on November 17, 2013

I like jamjams idea. I was thinking about the way bubbles form in beer, in micro cracks along the sides and bottom of the glass. If the jam lid isn't on tightly, the bubbles forming along the sides can work their way up and escape, while bubbles on the bottom get trapped and lift the jam. Maybe.
posted by bonobothegreat at 10:50 PM on November 17, 2013

How about this: the jar wall is somewhat thicker at the base, which means the inside diameter is a bit smaller. When you put the jar in the fridge the glass contracts, squeezing the jam upwards. Your fridge might even be cold enough to make the water in the jam start to expand, which just adds to the force pushing the jam up the side of the jar.
posted by Joe in Australia at 2:48 AM on November 18, 2013

Response by poster: My fridge seal is just average, I'd say.

I appreciate all the ideas! The thing that doesn't seem to fit into some of the hypotheses is: why now (as opposed to, say, two days ago when the amount of jam was about the same -- I only use a smidgen at a time, nowhere near enough to cover a piece of toast) and why not again? I checked the jam this morning and it was not floating, after nearly another full day of regular fridge-door opening.

Yesterday, on the other hand, there was a new air pocket forming about 2 hours after posting this question (and there was very little, if any, fridge activity during those 2 hours). That tiny, second air pocket went away while I was turning the jar about in my hands, without opening the lid.

If it were bacterial gas, I'd expect to see levitation again this morning, especially as the jar has remained unopened since before the second pocket began to form.

Damn it, jam. *appreciatively hugs and strokes jar of peanut butter*
posted by (alice) at 10:37 AM on November 18, 2013

I think it's maybe something like a jam meniscus. Maybe the cooling of the air in the jar as it sits in the fridge is just creating enough of a slight vacuum to cause the jam to crawl up the walls of the jar. What's the weather been like where you're at in general? Maybe you've got a jam barometer --- only when certain climatic conditions prevail is the vacuum forming.

I doubt it's bacterial off-gassing. Jams can get moldy after a while, but it's usually quite a long while. Because jam is so sugar-saturated, it's usually a pretty inhospitable environment for bacteria. That is the whole point of jam, preserving fruit so it won't spoil by sugar-saturating it. (And while I am not a microbiologist by any means, I really think it's impossible for it to be botulism --- botulism requires warm anaerobic conditions to grow. A substance that you've been chilling in a fridge for weeks while intermittently delving it with butter knives does not fit that bill.)
posted by Diablevert at 9:10 PM on November 19, 2013

Jam barometer! Interesting idea.
posted by zennie at 9:32 PM on November 19, 2013

I'm still not seeing how the formation of even an extreme vacuum in the space above the jam could cause air to be present in the bottom of the jar where there wasn't any before.
posted by contraption at 11:38 AM on November 20, 2013

Response by poster: jason_steakums: FWIW, the ingredients do include "apple pectin." I'm not sure if the last jar did, though!

While I'm not certain I posted my last question on the same day that the levitation occured, I checked the weather data for that day (March 1 '11) and it was not the same as the weather on the day of this second occurence. Not hugely different, but certainly more of a difference than between my second question and today, when there's been no further floating. Pressure was 1012.75 hPa the first time and 1008.33 hPa this time -- is that statistically significant? I have no idea.

Like last time, no response from the company (of course, it's only been a few days).

One of the weirdest parts of this, to me, is how utterly clean the empty space is. This jam is slippery and jelly-like, but the first jar was thick, sticky apricot and it was also utterly spotless at the bottom of that jar.
posted by (alice) at 9:46 AM on November 21, 2013

I emailed the people who make the jam. They got back to me today.
Although it may seem strange I have seen it happen on quite a few occassions while doing analysis on our products.

No need to worry, it is not outgassing or signs of spoilage. What actually happens is that when you slightly tip the jar to remove some jam with your knife, the mass of jam/spread left in the jar will move in the jar if the consistency is a certain set and there is a moisture layer between it and the inside surface of the jar.. On some occassions this traps an air pocket under the spread when you turn it upright again. You probably don't notice it when you put it back in the fridge but when you take it out the next day there it is. I don't notice it move when I am concentrating on my analysis and when I try to replace the spread into the jar it won't go back. Then I see the space underneath. If you make a hole through the spread and allow the air to escape it should slide back down in the jar.

Hopefully this explains that it happens sometimes and I have seen it with a few different flavours.
I do not find this particularly convincing (it was there all along and I just never noticed it?) but that is what they say.
posted by jessamyn at 12:53 PM on November 25, 2013 [2 favorites]

Be careful, Jessamyn. You don't want to anger the Conservationists.
posted by Joe in Australia at 3:12 PM on November 25, 2013

Response by poster: I received the same response (verbatim, except for the part about different flavours) today, as well. It doesn't quite jibe with what happened but I'm not going to pursue it with them. I think I might even try eating it.
posted by (alice) at 11:06 PM on November 25, 2013

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