When is it OK to eat moldy food?

My friend (and MAKE managing editor) Shawn Connally posted a chart about what kinds of moldy foods are safe to eat, and which ones are dangerous.
200908121607 My husband and I have battled continuously for years about whether scraping the mold off the top of -- well, anything -- makes it OK to eat, or if once a spot of green invades the top of a barely used jar of jam we've got to call it a loss and toss it out. I'm always willing to scrape off the top, cut off the moldy crusts, etc., and carry on with the meal. My husband, not so much.

Well, turns out the USDA has weighed in on the argument with interesting findings. My favorite part of the Safe Food Handling fact sheets is this chart on how to handle moldy foods (very, very carefully is not one of the answers).

Do you eat the moldy stuff?


  1. on cheese – just cut it off.

    related – after a while, butter tends to go bad from the outside in – you can actually see a ring of discoloration when you bisect the stick.

    i always scrape it off, rationalizing that the butter inside must still be fresh (or at the very least, fresher) than its sickly colored shell, but it always just doesn’t taste right. not anything that will ruin a meal or trash your stomach but still, not that fresh butter taste.

    oh and even less related – even though it says not to, you can totally re-pop the unpopped kernals of popcorn left in the bag by dumping some butter in there and rolling the bag loosly closed. found that out after accidentally buying a shitload of ‘low fat’ popcorn. i let it get halfway then throw a tablespoon or so of the good this in there. you get more kernals popped and it *gasp* actually tastes better than the styrofoam that is low fat popcorn.

    EVEN LESS RELATED, i babysat these kids about 12 years ago, whose parents were all diet this and non fat that. basically they had a house full of food that wasn’t worth raiding. fast forward, and those kids are like 17, 18 years old now, and they are about five foot one and perhaps 90lbs. i have no choice but to conclude that all the packing peanuts they fed em did it.

  2. That chart seems extremist. I just scoop out or cut off or rinse off the mold and keep eating – except for meats because I imagine that meats are full of creepy things to begin with. That chart basically says ‘throw out everything except bleu cheese’

    Also, why specifically say that molds in jellies and jams might be mycotoxins? I’m not a mycologist but wouldn’t any deadly mold contain mycotoxins? and if molds are mycotoxic – if they aren’t deadly/dangerous, why shouldn’t we just cut them off etc.?

  3. Ironically, meats hold a lot longer than say, dairy, from the danger standpoint

    Cutting the yellow off the butter doesn’t do that much, if it doesn’t smell it’s fine. I’m pretty sure rancid butter smells too bad to be edible long before it would actually get dangerous.

    Making your own sauerkraut or kimchi or seasoned oil without knowing what you’re doing is an easy ticket to botulism though.

  4. That chart strikes me as stupid and dangerous. It’s like a chart describing “When is it OK to play with dynamite”.

    I though every kid learns this in school, BUT: The mold is a special kind of fungus that actually grows inside the food. What we see on top is only the tip of the ice berg.

    Motivational story I read in the newspaper: Mom scrubs mold of jam, serves on bread. 3 kids dead.

    Motivational story 2 from a German MythBusters-clone: “Evil mold” can grow on top of good, French “edible mold” on cheese. If your Camembert has a green spot on it, throw it away.

    Tell Shawn (and the USDA) not to play with poison. If you can afford internet, you can afford to throw away good food. FFS, crawl into the garbage container behind a fine restaurant, if waste concerns you so much, but don’t eat bad food!

  5. Nutbastard, in support of your last paragraph: about a week or two ago I heard about a study where the experimenters fed people a salad with either fat-free dressing (the test group) or regular dressing (the control group), then stuck them for blood every couple of hours to see what nutrients they’d absorbed.

    The test group absorbed virtually NONE of the nutrients in the salad. The explanation was that most of the nutrients in vegetables are fat-soluble, and if you eat them without fat they break down without being absorbed.

  6. You still can’t beat the built-in five point alarm system, respectively: see, touch, smell, taste, hear, though I’m not sure what bacteria sounds like.

  7. Motivational story I read in the newspaper: Mom scrubs mold of jam, serves on bread. 3 kids dead.

    Daily Mail?

  8. If food doesn’t smell inedible I just eat it. I rarely bother to scrape mold off, unless it actually tastes bad (in which case I spit it out) or it’s floating free.

    It’s a system that makes sense to me… but, then, I believe in evolution.

  9. I heard a moldy jam at a Steely Dan concert one time and it gave me the runs. As in I runs-ed my ass outta there!


    BTW, I think the chart is very helpful. Thanks Mark (and Shawn.)

  10. Antinous @4 – It’s the USDA after all – you want they should use centimetres? You wouldn’t be a closet bolshie, wouldja?

    That said, I probably don’t even cut off a centimetre of cheddar over a bit of white surface mold.

  11. Everybody knows you can scrape a little mold off some cheese, but really, if you can afford a computer and a high speed internet connection and enough leisure time to read boingboing, you can probably afford to toss the moldy pork chops.

  12. As they say, eating red meat won’t kill you – it’s eating green, fuzzy meat that’ll kill you.

  13. Take the mould off with a spoon or a knife. If it still smells mouldy, take more off, or don’t eat it. Or if you’re my dad (didn’t die from food poisoning) eat it mould and all, while lecturing everybody who’ll listen about wasting food.

  14. this corresponds pretty much exactly with my long-standing intuitions about mould…

    on soft, liquidy, creamy, or porous things: bad
    on hard things or things that are supposed to be covered in mould: cut off any mould that it didn’t have when you bought it, and it’s fine!

    pretty obvious really, but still nice to see the official chart. haha.

  15. @nutbastard: Butter doesn’t go bad, exactly. While it does grow bacteria like anything else (especially if it’s salted), it gets inedible for other reasons long, long before that stage.

    As butter gets older one of its triglycerides breaks down into butyric acid which:

    – Smells bad
    – Is easily detectable (on the order of parts per million).

    So chances are pretty good that what’s happening is that the inner bit of butter which still looks good has nevertheless gone above your threshold of detection.

  16. Ah, PaulDrye, I was very curious why the salt would make it MORE susceptible to spoilage. But then you answered me in your very next post.

  17. Everyone should know by now that salt is a preservative. Look at the example of old people. Old people go to the doctor and the doctor tells them to cut back on their salt intake. Next thing you know they die. Eat salt, stay alive!

  18. Really, it all depends on how hungry you are. If you’re hungry enough you’ll dive into that dumpster with a spoon and fight off all comers to the death.

  19. Comparing eating de-molded food to playing with dynamite is like comparing a paper cut to a chainsaw wound.

  20. If you accidentally eat penicillin mold, you have to continue eating it once a day for 7-10 days, otherwise you’ll be engendering antibiotic resistance.

    Also, in general, if you come across hot dogs or luncheon meat, it’s a good idea to not eat them, even if they’re not moldy.

  21. fyi – butyric acid is what the Sea Shepherds throw on the whaling ships. Smells terrible, minimal toxicity.

  22. The chart seems lacking at best.

    Lots of foods, especially regional things like kimchi, technically spoil.

    Wine is another good example, or bleu cheese, or yogurt. Anything with a high level of moisture is probably not safe to eat if any form of mold is growing on it. Technically meats (solid cuts) would be safe to eat, and in centuries past it was the custom to let meat mold and decay before eating (the mold was cut off of course).

  23. Butyric acid is what smells bad in gingko fruit.
    Not really pertinent to the conversation, but hasn’t come up in conversation since I learned that two decades ago, so I think I’d better mention it now or else it may well be 2029 before I get to mention it again.
    Few. Thanks for letting me get that off my chest.

  24. With cheese, butter and bread, I scrape off the mold and keep eating (as long as it doesn’t stink; I trust my nose). Never got ill from any of those. Same with fruit. I’ve eaten the better-looking half of a fuzzy-looking strawberry many times and I’m fine. Moldy vegetables smell like hell though so I toss them out.

    With meats/seafood, I don’t take a chance. I eat it fresh and never stock up on it.

    Mmmmmm, foood…

  25. I’m a microbiologist rather than specifically a mycologist, but I can tell you that there are hundreds of thousands of different types of ‘mold’ fungi, some of which are edible, obviously toxic, or merely not a good idea to eat. That’s true of so many mushroom producing fungi, too. Generally, if there’s a visible fungus on the food there’s fungal growth all through the food, so if the fungus produces a toxin (and many of them only produce toxins under certain conditions) then the toxin is spread throughout the food, and many of those toxins don’t take a large dose to make a person sick.

    The most common mold fungi fall in the “merely not a good idea to eat” category, but can cause serious allergic reactions. Foods with live cultures often halt the fungal growth, which is why cheese and especially hard cheese is usually okay if you scrape off the mold. On meat, I’d be more worried about Listeria, which is a dangerous bacteria that can grow in many unlikely conditions including in the refrigerator. And you won’t get enough penicillin from eating or rubbing a wound with Penicillium to risk antibiotic resistance; the pharmaceutical form is considerably stronger and purer than the untouched fungal product.

  26. @madscientistk
    I know you won’t risk antibiotic resistance. That was a funny. If you were a mycologist you would get the humour, but sady, you’re just a microbiologist. Ask a mycologist to explain it to you.

  27. An inch of cheese all the way around is a lot of cheese to sacrifice.

    Also, I was dismayed to see that you have to chuck a loaf of bread that has a little mold on it. It’s quite disheartening to throw away an almost-complete loaf of bread, just because it has spots on one of the slices.

  28. @30:

    If you’ve got moldy seafood laying about, your problems are bigger than mold!

    Can fish get moldy? I’m sure it can, but why in heaven wait until that stage!?

  29. On bread molds: I never liked bread with green mold, but I used to get some white mold that I thought added an interesting flavor to the bread (though I didn’t think it was a strain or a habit worth cultivating). That is to say, I’d throw out bread with green mold, but I found the bread with white mold edible.

  30. ugh

    someone mentioned evolution- i am definitely thinking natural selection here folks. Don’t eat the nasty moldy food, it’s gone bad. Why risk it? An INCH of cheese is a problem?? throw it out!! i’m not eating white moldy bread, green fuzzy anything – if it’s questionable it’s OUT. If i don;t know how long it;s been in the fridge it’s OUT lol

    Why risk making yourself sick??

  31. Funny thing, I ate a moldy peach today. Zoiks. Gotta work on that will!

    The chart seems pretty obvious to me. Nothing extremist. People do get confused about cheese and ham. I know moldy strawberry sure can kill people, I just hadn’t thought out the “moist fruit” thing – hence my peach.

  32. I used to be from the “eh, who cares, as long as it doesn’t smell bad” crowd. But one 3-day bout of serious food poisoning (easiest 15 pounds I ever lost!) has put of off THAT practice forever.

    Now my stomach physically convulses at the thought of eating expired dairy. I throw out any yoghurt, soft cheese, milk, kefir, bread, meat, you name it, if it’s an hour past its printed shelf life.

    It’s not a matter of being cautious, it’s strong mental conditioning. I don’t even have a choice.

  33. Mom scrubs mold of jam, serves on bread. 3 kids dead.

    Well, then I won’t serve scraped mold on bread, that’s all, even when they cry for it!

    I throw out any yoghurt
    Actually, yogurt that’s been in the fridge long enough to become moldy is likely vintage yogurt: sell it on Craiglist.

    @ Antinous: I just did cut some mold off a piece of Jalsberg two days ago. Funny thing is that I have enough money now that it could to throw it away, just damning myself for being so stupid to let it get mold in the first place, but I’ve also been quite poor in my late teens and the habit dies hard.

  34. My rule is “When in doubt, throw it out.” Our evolution-derived response to bad smells and icky-looking stuff shouldn’t be ignored.

  35. Even though I can afford to write this from home via the interwebs, I can’t afford to throw out food. When it pertains to moldy lunch meat I just fry up a hot moldy hammy sammy, extra mustard, hold the mayo please. Can’t eat the internet.

  36. #6, lumpi:

    What we see on top is only the tip of the ice berg.

    Not necessarily. If you examine bread mould (Rhizopus) under a microscope, you’ll see that the parts that penetrate into the bread (the rhizoid hyphae) are very small (far less than a mm) compared to the visible parts on the surface.

    Motivational story I read in the newspaper: Mom scrubs mold of jam, serves on bread. 3 kids dead.

    That’s an urban legend unless you can give a decent citation.

    Fungal growth on jam doesn’t usually extend much below the surface due to the high osmotic potential (though I understand ‘diet jam’ is different).

    I personally have no problem eating bread, cheese, or jam that’s had surface mould picked off.

  37. I live in the Brie region in France — I was pretty surprised to learn that the white mold that forms the rinds of Brie here is so alive that it will actively grow over the cut surface of my Brie in the refrigerator within a day or two. Since it’s all the same color and consistency, I don’t get fussed…but wow. The bloom on the Brie I used to buy in the US was never that healthy!

    White mold on cheese? Ain’t skeered. Blue mold on bleu cheeses? no problem — it’s supposed to be there.

    Green mold? I might cut it off, but probably not.

    Orange or pink mold? THAT’s the stuff to steer very, very clear of. Anything with pink or orange molds (they’re slimy and wet-looking, too, so particularly unappetizing) — goes straight in the trash. Even the dog doesn’t get a go at that stuff.

  38. My grandmother (who grew up during the depression) told me the following about mold:
    – If mold appears on grains, fruits, or vegetables, then they’re bad and should be tossed immediately
    – If mold appears on dense preserved foods, other than canned foods, then you can use the food if you remove the mold, but ONLY if the mold is white. If the mold is green or dark yellow, toss immediately.

    She also said that if black mold appears, even just once, then you should scrub everything down and clean immediately, after removing the offending item.

  39. Aflatoxin deserves a mention, though I don’t believe that it’s necessarily on the foods that are visibly moldy. It is the kind of information that explains why a robust FDA is a good thing.


    To protect your kids have them eat (non-moldy) carrots.

    “Medical research indicates that a regular diet including apiaceous vegetables such as carrots, parsnips, celery and parsley, reduces the carcinogenic effects of aflatoxin.”

  40. Sipping on a tasty mix of fungus mixed with hops and malted barley. Ahh refreshing.

    Wait is yeast a mold? Better crack another one just in case it’s going to kill me…

  41. I eat moldy grapes and bleuets (blue-berries) all the time. It’s too much trouble to pick them out, and they add an nice winey flavor to a handful of fruit.

    You weaken your immune system and shorten your life when you throw out stuff you’ve evolved to eat. There is considerable recent research to bolster this idea – now some researchers are even saying people need occasional encounters with gastric parasites to be optimally healthy (http://jem.rupress.org/cgi/content/abstract/206/6/1395).

    Listen to MattF – you have a highly refined spoilt food detection system built right into your body!

  42. Mold on food is absolutely disgusting and I will throw it away immediately if I see any spots, growth, or discoloration.

    I won’t scrape it off, or dig past the mold to find the “fresh stuff”, because if yout food is growing new things, then no part of it is “fresh”. I don’t care how frugal you are, its gross.

  43. @34

    I’ve never had to deal with my own moldy/rotting seafood. But I’ve had roommates and also cleaned out office fridges…

  44. Beanolini @42, you’re thinking of the wrong microorganisms. The osmosis produced by the high sugar content of jams and jellies inhibits the growth of bacteria. Mold belongs in the fungi (different kingdom, different domain). It inarguably grows in jams and jellies — you’ve seen it yourself.

    Mold isn’t just a surface phenomenon. It sends down microscopic thready root structures that spread the contamination well beyond the visible mold colonies. Not all molds are toxic, but some produce toxins that have long-term rather than immediate effects. You can’t assume you got off scot-free just because you didn’t suffer respiratory paralysis or start voiding at all orifices. In short, it’s just not worth the risk.

    And speaking of respiratory paralysis —

    I can’t find any basis for Lumpi’s newspaper story: “Mom scrubs mold off jam, serves on bread. 3 kids dead.” I doubt one will turn up.

    In stories where everyone dies right after eating badly preserved food, the usual culprit is botulism. However:

    1. The bacterium that generates the botulism toxin, Clostridium botulinum, doesn’t form visible colonies.

    2. The boiling temperatures of jams and jellies that are concentrated enough to jell when they cool are well above what that bacterium will tolerate, so you’re not going to get a colony of it growing in an unopened jar.

    3. Once the jar’s been opened, its surface won’t have the anaerobic environment C. botulinum requires.

    4. No bacterium finds jams and jellies a congenial environment. The high sugar content kills bacteria by sucking the water out of them. (That’s the “osmotic potential” Beanolini mentioned.)

    Finally, while there are microorganisms that will grow in jam, I can’t think of any that kill fast enough to make a good story for the tabloids.

  45. Teresa, length of myceliae and penetration of media varies by species and substrate. Filamentous actinomycetes form flattened spheres in my compost pile, and circular colonies when grown on solid medium, for example.

    If you can see mold, you are typically seeing the fruiting bodies (spore production/dissemination mechanism) which indicates the presence of myceliae (the equivalent of roots and stems). The mycelium may penetrate the entire moldy object before generating any visible surface structure, or it may ball up in a concentrated mass called a sclerotia that is easily removed, or anything in between depending on mold species. Some species are self-limiting (the myceliae grow to a certain size and stop) and some will grow to their limit of their environment, but I seem to recall that most follow the same pattern as tree roots, which show markedly different rates of growth at different points in a tree’s life cycle but generally maintain a pretty specific proportionality between root mass and non-root mass once they’ve reached maturity. I might be remembering that last bit wrong, though; I’m an auto-didact.

    I’m willing to eat anything that does not seem inedible to me. It’s a zen thing.

  46. According to Charcuterie when dealing with dried, fermented sausages white mold is usually a *good* thing, while any other color of mold (blue, black, orange, brown, etc.) is cause to throw the sausage out.

  47. Fun fact about butyric acid- it’s what makes vomit smell like vomit!

    Course, you knew that already if you’ve ever smelled rancid butter….

  48. #53, Teresa Nielsen Hayden:

    Beanolini @42, you’re thinking of the wrong microorganisms. The osmosis produced by the high sugar content of jams and jellies inhibits the growth of bacteria. Mold belongs in the fungi (different kingdom, different domain). It inarguably grows in jams and jellies — you’ve seen it yourself.

    I know the difference between fungi and bacteria, thank you very much.

    Osmotic pressure does affect fungal growth- though admittedly not to the same degree as bacterial growth.

    Growing ‘on jam’ is also very different to growing ‘in jam’. There’s far more oxygen available at the surface (and most fungi are aerobes).

    In addition, it’s possible that condensation of water from the atmosphere can produce localised areas of much lower sugar concentration (and hence lower osmotic pressure) on the surface.

  49. Haha, snig, hilarious comments.

    glad you brought up aflatoxin, and i’m horrified to learn about the connection to carrots and parsley

    and from the cdc’s page on botulism, good straight-forward info, but did you know about the danger of baking potatoes wrapped in foil? weird. also, one way to avoid “wound botulism” is “by not using injectable street drugs”


  50. oh i’m an idiot – not horrified about about carrots and parsley, relieved:
    “Medical research indicates that a regular diet including apiaceous vegetables such as carrots, parsnips, celery and parsley, REDUCES the carcinogenic effects of aflatoxin.”

  51. If I remember well, the greatest gain in life span was achieved by the invention of the refrigerator. I’ve been told that refrigeration lowered our average consumption of bacterias, molds and their respective toxins. Which in turn lowered the stress on our digestive systems that resulted in less digestive cancers.

    Now what really surprises me is how sawer dough, cheese, sticky tofu… don’t kill you. I know it is because they are fermented with not toxic strains, but if you have ever seen the inside of a bakery it has not much to do with laboratory conditions. And in some bakeries the sawer dough is the result of a colony that can be decades old, why does the colony not get infected by a toxic species.

    And if you think the flora of sawer dough or wine are artificially created in controlled laboratory and then introduced to our food within a safe time period. Well it does not work this way. to start a sawer dough, the baker mixes some flour and water, set it a side to get contaminated from the air, let it ferment and if it does not produce the appropriated result starts again. For wine, before it’ industrialization one method to introduce the bacterias and mold was to mashed the grapes with your feet, and leave in the grape juice you athlete’s foot juice.

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