Half preserved

July 5, 2009 1:43 AM

I made a half-full jar of jam, is it safe to eat?

Never thought I'd ever ask a "is it safe to eat" question, but here I am.

I made some strawberry jam for the first time and I was only able to fill the last jar halfway full. The other jars were filled to 1/4" from the lip.

I gave it the same boiling and cooling time as the full jars. Due to the air pocket acting as a floatation device, I had to use a meat tenderizer as a weight to hold down the jar as it was boiled.

The jar lid dimple is depressed, so it looks like a good seal was made. There's some condensation inside the jar's sides, where the jam doesn't cover.

Will it be safe to consume, or should I toss it?

Also, the mashed berries seemed to separate during cooling. There's about 1" of jelly at the bottom of each jar and mashed fruit bits at the top — is that normal, in general?

posted by Blazecock Pileon to food & drink (23 comments total)

After a childhood full of home-made jam, all I can say is that we always ate it all, no matter what, and it didn't kill me.

Jam is preserved by virtue of being sterilised through heat to kill the bugs that are in there, and so full of sugar that there isn't enough moisture for any spores that land to grow. If anything does grow, it's almost always harmless mould. I regret to tell you that on the rare occasions when that happened, my Dad (the Jam Maker In Chief) would simply scoop it off with a spoon and pretend it was never there, and we would eat the remainder, which never tasted any different. Dad used to teach food science including microbiology for food technicians so I presume he felt it was ok.

Yes, our home-made jam used to separate sometimes. Totally normal.
posted by i_am_joe's_spleen at 1:52 AM on July 5

scoop it off with a spoon and pretend it was never there

I know that you're still alive, but that seems like a really horrible idea. When there's surface mold, there's probably lots of fungus buried in the food. I honestly can't believe that a food scientist would ignore fungus growth like that.

I guess I'm wondering if the boiling/sealing process can't complete properly with a half-full jar, or if the condensation is due to incomplete sealing. Is there something special about that 1/4" gap that helps ensure a sterile product and air-tight seal, all else being the same?
posted by Blazecock Pileon at 1:58 AM on July 5

Eat that one first. If you're really worried about it, stick it in the fridge and eat it within the next two weeks, but I am willing to bet that it's just fine, since it sealed properly.
posted by annathea at 1:59 AM on July 5

As annthea says, eat that one first -- that's always what we did with the last half-full jar when my grandmother made jam. (It killed me once, but I got better.)
posted by scody at 2:04 AM on July 5 [3 favorites has favorites]

I honestly can't believe that a food scientist would ignore fungus growth like that.

Believe it. I assume he identified it as a harmless mould, of which there are many. He's out of the country at the moment, or I would ask him why he thought this was ok. (We also would cut mouldy bits off the cheese, and spoiled patches off fruit, and eat the remainder. That's what made me strong and tough, not like you weak youngsters of today with your wiper and your hand sanitisers and anti-bacterial telephones...)

Google tells me that the USDA disagrees with Dad, so either the wisdom changed after the 70s, or his frugal instincts over-rode all else.

Now that I think about it, we would eat the half-full jar first too. The jam is really most aromatic and delicious when it's new anyway.
posted by i_am_joe's_spleen at 2:30 AM on July 5 [2 favorites has favorites]

When my gran made jam she just to put the left over bit either in a small desert/pudding dish, put it in the fridge and eat it first, or more likely, use it in a jam tart or something.

And she used waxed paper and rubber band seals with no problem with the rest and they would keep for ages with no mold (not that it ever lasted that long)

The big tip I know with home-made jam is never ever let any butter etc get into it by using a different knife / spoon etc as, as it's not filled with artificial preservative, it can't stand up to contamination.
posted by fearfulsymmetry at 2:44 AM on July 5

When there's surface mold, there's probably lots of fungus buried in the food.

I don't think that's going to be the case with a preserve... As was pointed out, the sugar saps any moisture from anything that tries to grow, preventing fungus growth except for on the surface where it can escape the effects enough (and probably, as fearfulsymmetry points out, needs a seperate seed, like the fat of butter).

If there's no mould on it at all, then you've nothing to worry about anyway. But unless you made it wrong, it's definitely not going to contain anything you can't see, and what you can see is most likely as harmless as a bit of mould on cheese.
posted by opsin at 4:59 AM on July 5

Eat it first, that's it.

My way of sterilizing jars is as follow: rinse the (carefully washed and dried) inside of the jars and the lids by pouring in a half glass of 95% -non denaturated of course- ethyl alcohol (don't know how that translates in terms of proof), closing and and shaking them.

Fill with hot (just-out-of-the-stove-hot-just-not-boiling) jam, close, turn upside down to kill anything remaining, let rest 5 minutes. Turn again downside up, beat gently to let jam residue fall down, let cool. Get startled by the loud pops as the lids get sucked inwards.

I don't boil the jars. It's cumbersome and actually I see little point in boiling at 100°C something that has already boiled for some time around 140°C.

I usually toss mouldy jam. On the other hand, I find that with this method mould is very rare (if at all).
posted by _dario at 5:16 AM on July 5

Boiling jars after they've been filled? Really?

Sorry, this is very unscientific, but from long home-made jam making/eating experience all I can say is 'chill'. I've never post-boiled my jars, I've left the tops off until the jam's cool because that's how my mum taught me, I've eaten the (non-mouldy!) contents years after its been made.

A quick check of my cupboard reveals a jar labelled 2007 with about a centimetre of jam in the bottom (I'd forgotten it was there). No mould, tastes fine.

I've found the greatest determinant of mould to be the dampness of the fruit when picked, though others may disagree.

And yes, the fruit lumps separate when I make jam too. There may be a knack to preventing this, but I don't know it.
posted by Coobeastie at 5:19 AM on July 5

Agreeing with the general advice here to eat the half-full jar first, and keep it in the fridge.

Also agreeing with the folks that scooping the mold off the top of a jar of jam and eating the rest is a bad idea. Okay, maybe a food scientist or microbiologist can tell you different about a particular jar of jam he has in his hand at that moment -- but we are not all food scientists, nor are we all microbiologists, and there is no way for the average person to know whether the mold on the jar WE'RE holding at that moment is the EXACT SAME mold that I am joe's spleen's dad saw and said was safe that one or another time. You might NOT get sick, sure -- but then again, you MIGHT, and the circumstances if you were wrong about that mold not being dangerous would really be unpleasant.
posted by EmpressCallipygos at 6:35 AM on July 5

Oh, and if you're making jam and you've only got a jar that you're only able to fill halfway, you don't even need to water-bath process it -- just stick it right in the fridge when it's cooled down from the cooking.

As to your other question -- whether it's normal for solid bits of fruit have floated to the top -- yep, that's just fine. Jam is kind of like Jello in that it needs to cool down in order to "jell", and any solid bits you have in it have time to float to the top before it jells the whole way. You can deal with this either by chopping the hell out of the fruit you're making jam from with a food processor or immersion blender (this is what I do) or just ignoring it.
posted by EmpressCallipygos at 6:41 AM on July 5

Just eat it now and it'll be fine. You can't keep it - there's still a lot of air in the jar and plain old oxygen will either discolour the jam or cause aerobic growth. Just open it, stick it in the fridge and eat it.
posted by GuyZero at 10:01 AM on July 5

Oh, as for floating fruit - in theory it's caused by syrup that's too heavy. In practice I don't think you can make strawberry jam with less sugar so it doesn't float (aside from low-sugar recipes). Mine always floats. scrump came by my house to get some plums and he gave me a jar of his strawberry jam - it had a bit of float to it. Other types of jam seem to do this less. My marmalade never floats. Cherry jam doesn't tend to float. In my experience.
posted by GuyZero at 10:03 AM on July 5

Boiling jars after they've been filled? Really?

Coobeastie, boiling jars after they've been filled is one way to process jam and other preserves for long-term storage.

Chilling things is fine if you're going to eat them right away, but for longer-term storage, some kind of sealing process is necessary.
posted by EmpressCallipygos at 10:30 AM on July 5

EmpressCallipygos - so my two year old non-jar-boiled jam has been preserved by magic? It's been in the cupboard for two years. Never in the fridge. Not in a cool larder. And this is what I expect of my jams!

The preservative in jam is sugar; that in and of itself should be sufficient preservative, though mould can still happen. I understand the point of boiling jars after they've been filled if there is no preservative in what has been put in the jar. But sugar is an excellent preservative.

I've just gone and checked my cookbooks, and such standards as Delia Smith's Complete Illustrated Cookery Course have no boiling of the jars. Really, if Delia Smith, my mum, my grandma and my Home Ec teacher agree on a cookery matter (and they rarely agree) it really has to be something fundamental!

Food safety is good, but this thread seems to be sliding into downright food paranoia. Eat the jam, Blazecock Pileon. It'll be great.
posted by Coobeastie at 11:13 AM on July 5

I dunno who Della Smith is but the USDA and the Government of Ontario and everyone all recommend that canned food either be treated in a water canner (for high-acid foods) or a pressure canner (for low-acid foods).

Yes, you've never died, but that doesn't mean it's universally safe. You haven't died in a traffic accident either but lots of people do. You're making the same rationalization as the guy who has a few drinks and drives home becuse he does it all the time and nothing's ever gone wrong before.

And this is what I expect of my jams!

This is not what home ec departments and food scientists expect. Or at any rate, it's not what they recommend.
posted by GuyZero at 11:58 AM on July 5

Going from that link and having a look elsewhere it's the acidity that prevents botulism from germinating, not the relatively low temperatures that a boiling water bath has. Botulism is the main fear in bottled/canned food (at least the most scary thing). A number of other bacteria again are inhibited by the acidity of jams.

Moulds form on the surface because the sugar is diluted, so that its inhibition of osmosis is no longer present. The rest of the jam, because of the high sugar content, is hostile to bacteria and moulds.

The single applicable PubMed citation I can find refers to norovirus. Nasty, but if you ate one of the berries before you made the jam you'd have come down with it too; nothing to do with the inherent properties of bottling.

As far as I can tell all of the information about boiling the containers comes from US and Canadian sources. The UK FSA has nothing in all its safety bits about bottling at all. My suspicion is that more people in the US/Canada bottle foods that do present significant dangers without this treatment (low acid, low sugar), so the advice is given to everyone to minimise the danger.

Yes, you've never died, but that doesn't mean it's universally safe.
My other grandma is the worst, most dangerous cook in the entire world, and hasn't died. I am well aware of the non-applicability of her food hygiene to things I want to eat.
posted by Coobeastie at 1:49 PM on July 5

We opened up the half-jar this morning, mixed up the bottom with the top, and spread a good thick dollop on pieces of toast. Yum yum. It was probably the best jam I've had since the time I spent in Germany ten years ago.

This actually turned out to be a good way to tell that the rest of the batch had almost the right consistency, which I was really happy about. I think I'll use just a shade more pectin next time.

We're in the Pacific Northwest and my allergies didn't start until I moved here a year ago. Apparently the weather here allows stuff to grow year-round, so I can only imagine the spores and bacteria floating around in the air in our home...

So I think I'll keep doing the boiling step for now, as it doesn't seem to affect flavour to any significant degree, everything I've read in canning literature from US, Britain and Germany seems to recommend this step, and I think it will help ensure that we get fewer moldy, infected jars.

Thanks to all for your help.
posted by Blazecock Pileon at 2:33 PM on July 5

The preservative in jam is sugar; that in and of itself should be sufficient preservative, though mould can still happen. I understand the point of boiling jars after they've been filled if there is no preservative in what has been put in the jar. But sugar is an excellent preservative.

So how does sugar create an airtight seal on the jar, then?....

It's not just about preserving the food, it's about creating a seal on the jar so as to prevent airborne contamination from sneaking in. That is what the boiling water bath does. Sugar prevents the food from rotting -- the airtight seal prevents mold from getting in. Those are two different kinds of "going bad."

I'm pleased that you've had such god luck going without this. However, a few anecdotes aren't necessarily proof of concept; similarly, I've never had a flu vaccination, and I've also never gotten the flu. However, I would not then go on to tell people that "because I've never gotten a flu shot, nor have I ever gotten the flu, this is proof that flu shots aren't necessary for anyone." All it means is "I've been really, really lucky."

It's not about being paranoid -- it's about me figuring that, if I'm going to go to all this trouble to make the stuff, I want to make forDAMNsure that it's not going to have ANY chance of potentially making anyone sick.
posted by EmpressCallipygos at 3:09 PM on July 5

The chances of you dying from it are pretty slim, since strawberry jam is relatively high acid (or should be, if you made it right), but what are you really gaining by pushing your luck? Half a jar of jam?

Sugar doesn't really enter into the calculus as far as preservatives go. It stabilizes color and shape, but doesn't keep it from growing nasty microbes.
posted by electroboy at 4:29 PM on July 5

My second post has no anecdotes in it; unless a lack of PubMed citations is an anecdote?

Airborne contamination is moot once you open the jar anyway.

electroboy - yes, sugar is a preservative. Sorry, but it is. Osmotic inhibition = hostile to bacteria and moulds. They're called "preserves" because they were invented to preserve fruit; and the way they do this is through the sugar.
posted by Coobeastie at 2:35 AM on July 6

Ah, it appears that it is. My mistake. Most of the sources I've read have said that it's more about color and shape when preserving whole fruit. Makes sense though, sealed jars of honey don't spoil, but that's partly due to the acidity.

The problem with nonsealed jars in this context, however, would be that your preserves would absorb moisture from the air, making your preserves increasingly less resistant to colonization over time.

My second post has no anecdotes in it; unless a lack of PubMed citations is an anecdote?

...if Delia Smith, my mum, my grandma and my Home Ec teacher agree on a cookery matter...
posted by electroboy at 6:29 AM on July 6

Airborne contamination is moot once you open the jar anyway.

...Well, yeah. That's why you put it in the refrigerator after you've opened it -- the refrigerator keeps things too cold for airborne beasties to survive anyway, so it's a moot point that the seal's broken.

But I had a thought -- you say that you don't boil the jars. Perhaps, do you instead turn the jars on their heads for a couple minutes first before putting them away in a cupboard? Because in some cases that actually is creating the vacuum seal right there.
posted by EmpressCallipygos at 8:26 AM on July 6