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Everyone in my family says that when you see white mold on jam or pickled goods, you shouldn't bother with throwing away or removing the mold. All you have to do is to mix it back into the rest of what's in the pot. Here is an example:

enter image description here

I would like to know if it's a myth, because I feel something evolutionary in me that tells me simply mixing it back into the water is a bad idea.

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Bar Akiva
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    This is one family tradition that needs stopped before someone gets seriously ill or worse. Simply, no, please do not do this. Do not think it is OK. Do not even hint to others that they can do it. – dlb May 28 '17 at 15:34
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    I would say that "*everyone in your family*" are **wrong** regarding this... – Baard Kopperud May 28 '17 at 19:41
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    It seems like this family has evolved to cope with the method! – Volker Siegel May 28 '17 at 20:30
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    @VolkerSiegel It only takes one instance of a more harmful strain for tragedy to strike, very similar to people who have reused canning lid, left potato salad un-refrigerated, and raw meat on the counter overnight for years with no problem. Play the odds long enough and you will lose. – dlb May 28 '17 at 22:25
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    @dlb "Raw Meat on the counter overnight for years" Did it eventually grow back into a sentient creature and walk out? – Sidney May 28 '17 at 22:27
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    Trust me on this. You don't want to know this for the same reason I know it: **Do not eat anything even slightly moldy**. Just don't. – Todd Wilcox May 29 '17 at 05:53
  • I fail to understand why this is an issue at all. Is this some kind of immortality jam, or super-powers-giving jam? Other than that I honestly cannot comprehend why someone would save some jam taking the risk to be sick, or ill, or to die (by hand-waving that it is probably safe to do this or that with the mold). Do not even breathe it in. – WoJ May 31 '17 at 08:15
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    Something I think everyone should remember: The concern here is not whether molds are dangerous threats to the sanctity of health and diet. The concern is whether eating an ***unidentified*** but apparently fungal substance is hazardous or not. Many fungi are harmless or even edible; others are deadly and almost untreatable. Also, people have varying susceptibilities to the various proteins and mycotoxins produced by fungi. – can-ned_food Jun 01 '17 at 05:16
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    Furthermore, as a more general comment, it should be said that scraping off the visible fruiting bodies of a fungal colony does nothing to the almost invisible mycelia innervating the substrate — pickles, wads of fruit jam, whatever. Indeed, you should always use the odor of a foodstuff to assist you with ascertaining its edibility. – can-ned_food Jun 01 '17 at 05:21
  • @can-ned_food: I was with you until "*you should always use the odor of a foodstuff to assist you with ascertaining its edibility*". First, one should never breathe mold in. Then your nose is not a good indicator of anything. We have evolved to avoid certain odors and tastes (fecal, bitter, ...) but this is more a last safety net than anything else. – WoJ Jun 01 '17 at 13:02
  • @WoJ Breathing mold: especially the spores. Good point. Even fungi that wouldn't survive in your nasal or bronchial membranes could cause epithelial distress and irritation. And if you inhale large enough droplets from anything, they could always carry bacteria or other microbes. I meant if there were no visible spores or fuzz, then sometimes the odor of fungal or bacterial activity could be detected: alcohols and acids and such pieces that they excrete when they digest larger molecules. – can-ned_food Jun 01 '17 at 18:39
  • If you are obtaining the odor from an iffy item in a jar, be sure not to insert your nose directly in the mouth. It is better if you don't even position your nose over the opening at all, but off to the side. Use your hand to waft some of the vapors out of the open container. – can-ned_food Jun 01 '17 at 18:43

7 Answers7

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Unless there is good reason to assume it is not mold/bacterial colonization, but some other precipitate as explained in other answers:

There is no scientific reason at all to assume that such a method is safe, certainly not for any random pickle made by any random recipe spoiled by any random white mold found in any random environment. While some very acidic pickling liquids might kill the mold or bacteria, it will not deactivate existing aflatoxins or bacterial toxins.

rackandboneman
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    As a side note, mold will often only be on the surface of the jams or pastes, so it's usually safe to scoop the mold on the surface and use the parts that are not touched by air. (sorry if the sentence sounds odd, I couldn't find the exact words to describe it) Also, mold will often times just stink and stink really bad. So... If it stinks, I send it into the trash bins. – John Hamilton May 29 '17 at 12:52
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    @John Hamilton Separating a spoiled layer and discarding it (as you suggest) is the opposite of mixing it into the food (as the question suggests).... – rackandboneman May 29 '17 at 13:53
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    @rackandboneman: That's probably why John introduced his comment with "As a side note, [...]". – ruakh May 29 '17 at 14:53
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    rackandboneman Easy to explain why trival matters get so many upvotes - people read the question, not believing someone is really asking that and then in horrified amazement click on upvote, in the hopes NO one will ever EVER think it's okay to do this! I also got a big belly laugh at some of the other humorous comments. I needed that today! :D – Jude May 30 '17 at 06:11
  • @JohnHamilton but if the top is *covered* in mould you won't get the bits from round the edges, at least without contaminating the bulk – Chris H May 30 '17 at 12:18
  • @ChrisH If the amount is small enough it won't matter all that much if it's mixed in properly. Though this will mean that it'll go bad faster than last time, so better get to consuming the whole jar. – John Hamilton May 30 '17 at 14:19
  • @JohnHamilton yes, it will go off very quickly again – Chris H May 30 '17 at 14:20
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    @JohnHamilton All the recommendations I've seen are that one shouldn't just scoop mould from the surface of soft foods, because the mould can penetrate deep into the food. Perhaps the high sugar content of jam makes this safe but, for example, fruit with surface mould should be discarded. – David Richerby May 30 '17 at 16:42
  • The perverse approach of that tradition might be one of dilution vs tolerance... atrocious idea I'd say :) – rackandboneman May 31 '17 at 18:55
  • Dilution? I can see how that manner of thing would come about. Of course, as you know, they aren't actually diluting anything but the visibility, but that does help explain it. – can-ned_food Jun 01 '17 at 05:25
  • Even more nefarious, the idea might be "if X gram of Y makes you acutely sick, dilute it to a fraction of X". – rackandboneman Jun 01 '17 at 07:51
  • @rackandboneman - Pretty sure you are getting into Holistic territory there... – SeanR Jun 01 '17 at 08:12
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Well, let's start from the top. You mentioned "Jam and Pickles," but these are actually two very different environments for the growth of things like molds and bacteria.

In terms of jams (but also mold on foods in general)

Some people have already mentioned that you might be seeing something other than mold. If it IS mold, the USDA recommendation is to chuck it due to potential mycotoxins.

The USDA actually has a lovely table drawn up of recommendations for what to keep and what to toss when you do see actual mold in your food.

Jams and Jellies

Discard

The mold could be producing a mycotoxin. Microbiologists recommend against scooping out the mold and using the remaining condiment.

Personally, I recommend following the USDA's guidelines on eating (or more generally, not eating) food with mold. This doesn't mean I always do so myself (often if it's just a very small spot, I get annoyed and end up carefully scooping it out, even knowing I shouldn't), but it's what I'd be comfortable recommending to someone else. Honestly there's enough other ways to get food poisoning that are risky but may be deemed worth pursuing for achieving something you can't really get without taking that risk (and, ideally, ways to help mitigate those risks, like deep freezing with sushi, etc); I'm not really sure trying to not throw away some jam is one of them.

Granted, the picture doesn't look like mold to me, and I would tend to agree with the other comments regarding the picture in question likely being pectin or crystallization but it's honestly hard for me to tell for sure from that particular image, personally.

Pickles: mold or… Kahm?!

Obviously, when talking about pickles, you shouldn't be seeing pectin on the surface. But what you might see with a pickling process that can sometimes be mistaken for mold is yeast! Kahm yeast, to be precise, is a somewhat common pickling issue when things don't quite go perfectly. If it is Kahm yeast, it's considered harmless.

Still, most places recommend scooping it out as much as possible (within reason) rather than mixing it back in. Not because it's going to hurt you, but because it will affect the flavor if you stir it back in.

So that seems to be another point against the "always just mix it back in!" myth, if we start from the assumption that it formed based mostly on the mistaken identity of things like Kahm that aren't actually mold.

So how can you tell if you have mold or yeast? (or both??)

Kahm yeast shown in a jar and on spoon
image credit: Cultures for Health - White Film on Cultured Vegetables

Mold usually distinguishes itself by appearing "fuzzy" (growing up from the surface a bit with fuzzy tendrils) as well as growing tendrils into whatever it is growing on/in (often these are not very visible, depending on the stage of growth, which is another reason to throw certain things out when they get mold infested, because it will be more than just on the surface). Kahm yeast, on the other hand, is usually described as looking like a relatively flat coating (that may have bubbles or ridges formed under it due to the fermentation process). Kahm yeast is always translucent (depending on thickness) white to light cream in color. Thicker cultures of Kahm yeast may appear less "flat" and more rough, but the basic principle still applies: it's not "fuzzy" like mold.

I did actually find one interesting picture that shows the growth of some mold on top of a culture of Kahm.

If you actually do have mold growing on something

…and not just some part of your jam separating out or Kahm yeast growing on your pickles, then no, stirring it back in is about the last thing you would ever want to do. If the mold is creating mycotoxins, you've just mixed them back in to the rest of the jam. Even if you did manage to kill the mold, the laced food could still poison you: mycotoxins are toxic chemicals produced by the mold and won't go away simply because the mold itself is (or appears to be).

Also, you've now helped the mold spread, even if at first it appears to be gone from the mixing process. Where there's mold you CAN see, there's usually mold you can't see yet. This is part of the reason for the recommendation to cut an inch around any mold growth on foods that are generally considered to be safe to eat after the mold on them has been properly removed, like cheese.

taswyn
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    I'm glad you included the quote about discarding jams and jellies with mold. People think if the remove the moldy part, it's safe. But mycotoxins produced by mold is never safe. – Jude May 30 '17 at 06:20
  • Cut an inch around the mold on cheese? Unless it's a nice large wheel there'll be precious little cheese left :-( – Tom Goodfellow May 30 '17 at 07:49
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    @TomGoodfellow The USDA req is: "Cut off at least 1 inch around and below the mold spot." I tend to cut shallower (shhh), but I do cut at least the surface away starting **at least** an inch away from the mold colony. Partly, this helps slow/reduce the recurrence of mold, from spores that aren't visible but are present around the main colony. Often if it's an uncased hard cheese, or a surface with the casing or rind removed, I'll just shave that entire surface after removing the main mold colony itself. And change out whatever it's being kept in. It's rare that I need to, but life happens! – taswyn May 30 '17 at 16:47
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I have no idea about pickles, but if your jam has mold on top, the last thing you want to do is mix it into the rest of the jar.

If you just have a couple tiny spots of mold on top of the jam, or on the jar above the jam, you can even completely remove the mold (generously - i.e. excise a little bit extra all around the moldy patch too), & the rest of the jam can be still good.

However, your picture is of some odd looking mold. I wonder if it is really mold and not some other substance.

If that is jam - marmalade? - that white stuff might be something else that separates from homemade jam if it is old. Some kind of pectin or sugar content coming out of solution. It's often a little crunchy, and does not smell or taste moldy, nor is it ever "furry". Whatever that substance is, (not mold but other whitish exudate from jam) I do mix it in with the rest of the jar. But you have to be sure it's not mold, or that would ruin the whole jar.

If your picture is of pickles...I don't know what that white stuff might be.

Chris Cirefice
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Lorel C.
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    Agree re surplus sugar precipitating out / crystalizing in jams & marmalades, and that's what this one looks like. Perhaps in some pickles salt can precipitate out similarly? – abligh May 28 '17 at 20:04
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    @fluffy I think the idea is that we just sit in our dark basements staring at the computer all day and night, not having time to make sure we get rid of spoiled food. Or that we're so involved with the computer that we can't keep our fridge in order. Or, I have no idea. I edited it out of the answer, in any case. – Chris Cirefice May 30 '17 at 13:29
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    I'd be careful about recommending just cutting the mold out, as it depends so much on the moisture content and porousness of the food. Mold is not always visible, and depending on the food, invisible parts can survive under the surface. For example, it's relatively safe for hard cheeses, but definitely not for bread. Others like jam are somewhere in between; some say it's ok, some others (including the USDA) recommend throwing the whole lot out. – congusbongus May 31 '17 at 02:21
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You assume it is mold, but actual mold in jam bottles are rather rare. What you more often get is Congealed Pectin or crystallisation of the sugar crystals.

Remember that sugar is very much a preservative just like salt. If you use the correct amount of sugar than the sugar will inhibit mold growth to a large degree.

So unless there was truly negligent cooking going on, it probably isn't mold.

Neil Meyer
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    I've certainly had jam go mouldy outside the fridge. – David Richerby May 28 '17 at 17:10
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    How do you then know what is mold and what is sugar? – Bar Akiva May 28 '17 at 17:32
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    You could always put a bit of it into some warm water and stir it. If it dissolves, it's sugar. If it doesn't, it's mold. – fluffy May 28 '17 at 20:02
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    @Bar Akiva, experience. ...Mold tends to grow in discrete patches on jam, starting out as dots, which become bigger & somewhat furry over time, and often have some color other that white (gray, black, bluish..., etc.) Whereas this sugar or pectin phenomenon occurs in more of a film pattern on the jam surface, is only white, and has a crispy brittle appearance (never furry). When disturbed, it sort of cracks a little sometimes. [I've made a thorough study.] ..it also doesn't have odor or taste. – Lorel C. May 28 '17 at 21:26
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    "If it dissolves, it's sugar." To anyone going by this rule, note that when something *dissolves*, the resulting mixture (solution) is always clear (unless it's too dark to see through). If you end up with a *cloudy* mixture, that indicates that the solid has *not* dissolved. So, for example, flour does not dissolve in water. – Tanner Swett May 29 '17 at 01:43
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    Mold _used_ to be rare in jams, but with modern food trends (low calories, no preservatives) this is no longer the case. – MSalters May 29 '17 at 12:47
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    Twice in as many years I've opened a brand new jar of commercial raspberry preserves and found a patch of mold growing on top. The standard, full-sugar, non-organic, US grocery store type, opened within a few days of purchase (and *well* within the "best by" date). – 1006a May 30 '17 at 04:26
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    @MSalters I'm not sure there was ever a lot of preservative in jam, besides the sugar. More significant in this case is that people now tend to keep their houses warmer and modern houses tend not to have a cool, unheated pantry for food storage. So, now, your only choices are cold in the fridge or distinctly warm in the rest of the house. But I agree that things like ketchup have had preservatives removed from them. – David Richerby May 30 '17 at 16:46
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    @1006a You really need to report that to the appropriate regulatory agency/agencies. – RockPaperLz- Mask it or Casket May 30 '17 at 17:39
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For the jam (and honey), if it's crystallization, you can also heat the whole jar gently in a double boiler. Put the jar in a sauce pan with enough water to go up to the shoulders of the jar. Heat gently. Very gently. Stir if you can.

This is iffy with commercial products because you can melt the plastic containers (and also of little value because they're usually not worth saving), but a good preserved fruit or a good honey is worth putting a little effort into keeping. Be careful to just heat it enough to break up the crystals (don't get it anywhere near boiling), any heat at all will do a little cooking which it really doesn't need (storing it in Tennessee over the summer is enough to cause deterioration).

sighthoundman
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For food in an aerobic environment it’s probably always the case that these should be thrown away because of the health consequences that it can have on you.

vizz_bob
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Useful advice on storing jam from Nigella's site:

Home-made jam should be stored in a cool, dry place away from direct light and used within 12 months of making. Once opened the jar should be stored in the refrigerator and used within one month. We would suggest discarding any jars of jam that have mold growing on top.

Tom Goodfellow's comment is incorrect. While some types of cheese are deliberately infected with mold as part of the maturation process (for example Blue Stilton) and are perfectly safe to eat. Eating other types of cheese which have had mold growing on it is a bad idea because this type of mold produces toxins which spread throughout the cheese. Cutting off the moldy parts will not remove the toxins. I was told this by a food scientist.

Catija
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