Importance of Natural Resources

Food Mold 101

You know when you got, like, three-quarters of a loaf left, And then you see that little blue-green fuzzy spot. And you’re like, aagh! Should I? Should I not eat, but… You know, you probably shouldn’t eat it. But why? And why can I eat this? But not this? It’s a moldy world out there, especially in the kitchen. And we have answers for you. [Intro] Food mold, like all molds, are microscopic fungi. They grow from tiny spores that float around the air all the time, And they’re all around you in this very moment. Seriously. Mold spores are between three and forty microns long. Your hair is about a hundred and twenty-five microns wide. So tiny. When conditions are right, there’s enough moisture, warmth and nutrients, Spores will set up shop. Unlucky for us, mold prefers the same kinds of temperatures that we prefer, And even the coolness of a refrigerator won’t prevent mold from forming eventually. Let’s say our mold has found a delicious peach on which to grow. In its early stages, the spore releases root threads of the mold fungus deep into the fruit. By the time you see the first signs of mold, those threads, called mycelia, have already penetrated the inner depths of that peach. These roots are difficult, if not impossible, to see. The signs of mold, whether it be weird fur, green dots, or white dust, are a result of the stalk of the fungi rising above or sitting on the surface of our, now not so delicious peach. The spores that form at the end of the stalk are what give mold its color. Mold is an efficient organism, growing quickly, as enzymes released by the mycelium break down whatever organic matter it has invaded. Unlike other fungi, mold digests its food first and then eats it, allowing it to grow at a faster pace. Now, you may have heard that mold isn’t dangerous if you just cut away the ugly parts and eat the rest of the food. This is generally true with harder foods like apples, potatoes, onions and hard cheeses like cheddar and swiss, where the mycelia can’t quickly penetrate their host. But I would suggest not cut or scrape away the mold off of soft cheeses, berries, meats, and other produce. You may very well become ill if ya eat that kind of thing. The reason is mycotoxins. Poisonous chemical compounds produced by several kinds of mold. Mycotoxins are produced around the mycelium and not only can they survive a really long time, But most aren’t even killed when the food it has invaded is processed or cooked. The molds that produce mycotoxins are mostly found in grains and nuts, but have but have been known to invade celery and other produce, as well. One of the most dangerous mycotoxins is called aflatoxin, which is produced by two kinds of mold. This naturally occurring poison which has been known to cause cancer is typically found in field corn, wheat, oilseeds, and peanuts. In fact, many scientists believe that those dangerous peanut allergies we’re always hearing about are a result of a reaction to aflatoxin, not the peanut itself. Other foodborne molds may cause less severe allergic reactions, rashes or nasty infections. Of course, some molds don’t produce mycotoxins and are totally safe to eat. Notably, the ones you see in some smelly cheeses, like blue cheeses, and gorgonzola and stilton. *grossed out Hank* These are actually created by the introduction of specific mold spores. One of these, penicillium roqueforti, comes from the same genus of fungi used to make the group of antibiotics known as penicillin. The mold in these cheeses breaks down complex organic molecules into simpler ones which smoothes out the fiber structure of the cheese, and also results in their unique flavor and smell. But moldy cheeses are not immune to other molds. So be careful next time you’re about to dig into that six-month-old block of Roquefort. So let that be a lesson to you and thank you for watching this episode of SciShow. If you have any questions, comments, or suggestions you can find us on Facebook and Twitter and down in the comments below. And if you want to keep getting smarter with us here at SciShow, you can go to and subscribe.

Reader Comments

  1. I have a very piqued sense of smell for moulds, I can smell the mould in mouldy food long before it's visible. Because of that I some times cut away the mould and then smell the part I'm eating before putting it in my mouth. Tomatoes I usually cut 1/2 of them away for a tiny speck and stone fruit I cut through to the stone. Any more than a couple of mm of mould and I trash it, and with bread I just won't touch it because usually if there's a spec or smell anywhere on it, it's everywhere to the point that I'd be spitting out every second mouthful.

  2. Aflatoxin was also likely the cause of the deaths of the first born chronicled in Exodus, the previous plague (hail) caused damage to the wheat still in the field, which was then harvested and stored. Due to it being harvested early and the wet conditions mold grew on it. The first born were traditionally given larger shares of food when there was a shortage so they ate more of the mold and died.
    I know Bible is not a scientific text, and the reasons given for various things happening are considered myth or superstition, but the events themselves are usually very plausible even without divine intervention.

  3. Thanks for this video. It settled a debate between my parents and me. We are not going to eat the moldy mozzarella.

  4. I like stilton,eaten it many times,but I'm allergic to penicillin. How is it I can eat mouldy cheese and not get the severe allergic reaction I would get with the penicillin antibiotic?

  5. Is the mold on cheese, killed? If it's live, then it would make other types of mold less likely. Just like bacteria compete with each other and interfere with each other, so does mold, compete with other mold and also with bacteria. So cheese with safe to eat living mold colonies on/in it IS notably more safe from other kinds of mold and bacteria that are potentially more harmful.

  6. Hi. Your link to the references doc takes me to an add to buy instagram followers. Could you re-upload it or something please?

  7. 1. It would be good if you could list a lot of the good moulds that spontaneously grow on different foods (rather than those introduced to the cheeses); if there are any?

    2. Does each species of mould 'attack' only one type of food?

    3. The scary part of this clip seems to be that the roots of the mould may've already permeated the food without showing on the surface yet – is that possible?

    I used to occasionally eat slightly-mouldy bread thinking I was getting something akin to penicillin (that was in my ignorant early-20's), but I don't remember getting sick from it. Hence my question 1. above (any other good moulds apart from the 'cheesy' ones?)

  8. Everytime I take a bread slice, I have to inspect the loaf in the bag for at least 30 seconds. Touching and eating blue bread by accident is horrifying.

  9. I worked with Aflatoxin B1 in contaminated samples of corn and peanut paste, as part of my third year project as a chemistry student at university. Highly dangerous stuff as Aflatoxin B1 is the most and carcinogenic form of the mycotoxin, and I was allowed to have a whole fume cupboard to myself in the lab. This year I'm hoping to work with botulinum toxin as part of my fourth year master's project.

  10. You are suprisingly brilliant. But you forgot to mention that the molds will affect all people differently. The older weaker people, the sick, children and others are at greater risk than a super healthy hardbody. Moldy cheese is good. Sub us back.

  11. I came here bc I just got a bad case of disorientation after spreading some Roquefort on some bread. The Roquefort (which had been opened and wrapped in the fridge) was about a month old. Thanks for the insight.

  12. fun fact, aflatoxin is used to bleach white flour. So while we are throwing out our enzymatically predigested moldy fruit we are scarfing down the most dangerous part in our breads and noodles and cakes etc.
    It's also interesting that fruit is the sweetest and most delicious where there is a little mold on it, before it goes bad or is overtaken. So… is there some long forgotten symbiotic relationship between mold, fruit and us that used to be part of our healthy immune system or at the very least an addition to our nutrition?
    I'm thinking yes, and I'm interested to find it.

  13. i forgot to wash my lunch box with a fish in it and after one or two weeks when i opened it there was a white cottony-like thing inside. it doesnt smellef good, and now that i think about it it was probably a mold lol. and i washed it with my bare hands XD

  14. When I was little my mom gave me moldy bread but it was tiny mold I didnt notice until my older brother spotted it

  15. I ate some cake late at night and noticed in the morning that there were yellow mold dots on it. I will probably be dead soon. Goodbye SciShow.

  16. Thank you from our year six class in Queensland for a very informative exclamation on how mold grows and please talk a little slower next time 🙂

  17. I decided to watch this AFTER I ate a moldy tomato… goodbye cruel world…lol
    Seriously though, I think I'm going to die (placebo effect). Lol

  18. I made some burgers myself and only noticed after building them fully together and cooking that the bun had some tiny blue spots on it…

    It's… really great having to throw out $10 of dinner

  19. I left my coffee grains and filter for a couple days and when I opened it was filled with mold then when I threw it away a cloud of dust blew everywhere. Disgusting

  20. 2:57 But does Hank like Brie and Camembert, which also have mold and don't advertise it with a lovely blue-green hue?

  21. Roquefort is French, don't pronounce the 't' at the end, also, pronounce the whole word differently than how you did, Hank. Thanks 🙂

  22. I'm allergic to peniciliium mold, and I can't have penicillin and I can't eat any cheese that is made from the mold. I'm also so allergic to the mold that when citrus fruit starts to go bad, I will have a pretty severe reaction.

  23. I think most of the produce you buy in the stores is MOLDY. I think most produce coolers at most grocery stores GET A CERTAIN TYPE OF MOLD that you can identify by smell and then our produce smells like that! YUCK. I made a video about moldy greens from two different companies and how they SIZZLE when washed in hydrogen peroxide.

  24. I throw away a lot of bread because of mold. I was thinking of building a bread box including an ultraviolet lamp. Wouldn't that stop mold?

  25. Where can I find some of this good mold stuff you're talking about because it is absolutely delicious in my cheese and on my chicken fingers.

  26. When your looking for a simple answer of a yes or no if its safe to eat blue cheese but you gate an 3 minuit video

  27. My mom:"why did you eat my sandwich that i put in the fridge" me:"mom…… You put it in there 2 weeks ago"

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