Articles, Blog

Food Mold 101

August 19, 2019

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.


  • Reply Romirates November 10, 2015 at 5:54 pm

    Remember to eat your Roquefort with a delicious baguette 😀

  • Reply maxine austin November 28, 2015 at 4:13 pm


  • Reply Nikki Bishop November 29, 2015 at 8:51 pm

    Roquefort = 'rock fore'

  • Reply etmax1 December 18, 2015 at 2:06 pm

    Hank, The 't' at the end of Roquefort is not pronounced.

  • Reply etmax1 December 18, 2015 at 2:14 pm

    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.

  • Reply define alive January 6, 2016 at 2:45 am

    Moldy Peaches listener?

  • Reply Rusty Shackleford January 20, 2016 at 9:18 am

    Would Penicillin be a mycotoxin we can tolerate? Or is it classified as something else?

  • Reply richard reeves January 24, 2016 at 10:54 am

    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.

  • Reply swirlingtides February 1, 2016 at 2:07 am


  • Reply Scarlet Goose February 16, 2016 at 12:54 am

    I probably shouldn't have watched this while eating dinner

  • Reply Katie Westendorf March 22, 2016 at 11:15 pm

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

  • Reply Lorand Deka March 23, 2016 at 2:19 pm

    Mmmm I suddenly have a hankering for some Danish blue right now.

  • Reply the bobo March 29, 2016 at 4:12 am

    wish ergot grow easy

  • Reply P Heart March 30, 2016 at 5:20 am

    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?

  • Reply The Seleuf April 12, 2016 at 6:13 pm

    I want answers! Give me answers! o/

  • Reply Nestor Hernandez-Green April 13, 2016 at 1:57 pm

    I'm liker number 10k!!!

  • Reply Ty Wood May 4, 2016 at 4:56 pm

    Im taking a shit so the beginning of this video was a little weird.

    3/4 of a loaf

  • Reply truepurpl e May 12, 2016 at 4:46 am

    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.

  • Reply pcuser80 May 27, 2016 at 10:12 pm

    Roquefort on a roll

  • Reply tigris May 28, 2016 at 1:13 pm

    FFFFFUCK mould makes my skin crawl

  • Reply gusgous June 19, 2016 at 12:30 pm

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

  • Reply forestsoceansmusic July 15, 2016 at 2:21 pm

    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?)

  • Reply Kuroda Cursus July 18, 2016 at 11:02 am

    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.

  • Reply Drifter August 1, 2016 at 7:13 am

    I LOVE Blue Cheese. Thank God for mold.

  • Reply The Fn Man August 7, 2016 at 2:35 am

    Now I can see why there is a chance that mold can end up in an unopened bag of bread.

  • Reply CranialAxe August 13, 2016 at 1:08 am

    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.

  • Reply jonah holmes October 4, 2016 at 6:08 am

    2:09 mycelium – isn't that some minecraft shit

  • Reply Michelle Ong January 30, 2017 at 11:46 pm

    does cornstarch rot?

  • Reply Peyton Clarke February 14, 2017 at 3:28 am

    This vid is great GOOD JOB

  • Reply Julia Becker February 15, 2017 at 10:55 pm

    Thanks for the information, now I guess I wont be as completely grossed out because my dad loves bleu cheese……… 😛

  • Reply June Zhang March 8, 2017 at 6:57 am

    I just ate these moldy bagels for lunch today.

  • Reply drqazlop March 12, 2017 at 4:41 am

    these are not the answers I wanted

  • Reply Ashri Fisher March 16, 2017 at 3:21 am


  • Reply Michele Dicristoforo March 23, 2017 at 12:06 am

    wow he talked fast! Cool video wish it had more. i like it.

  • Reply Scott Velez April 14, 2017 at 10:56 pm

    If bread is rotten, chuck it in the crematorium.

  • Reply Dat Guy April 23, 2017 at 6:04 am

    Freaking love Blue Cheese.

  • Reply kurikuraconkuritas April 23, 2017 at 6:18 am

    huitlachoche is fungi grown in the corn. and it's mmmm delicious

  • Reply Adrian Padalhin April 24, 2017 at 2:29 pm

    Please do Scishow Food… ?

  • Reply HyρerБ2002 May 4, 2017 at 11:19 pm

    That moldy peach has a face.

  • Reply ChefGiovanni May 10, 2017 at 2:07 am

    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.

  • Reply cierra price May 14, 2017 at 1:24 am

    damn…..I like bleu cheese. ?

  • Reply William Caballero May 21, 2017 at 10:28 pm

    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.

  • Reply BlueLight June 7, 2017 at 4:24 pm

    Hey baby, I digest my food, THEN eat it. It helps me grow faster 😉

  • Reply ThatFancyMoos June 14, 2017 at 1:41 am

    that means as soon as you pick that froot from bush or tree it is instantly decomposing

  • Reply Adrian Brogan June 28, 2017 at 7:10 pm


  • Reply mirzamay July 2, 2017 at 5:16 pm

    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.

  • Reply Thom McHugh July 3, 2017 at 7:16 pm

    LOL, life causes cancer.

  • Reply No Name Provided July 24, 2017 at 9:31 pm

    So which molds do I eat and which molds do I avoid? How do I identify them?

  • Reply Pororo Penguin July 29, 2017 at 4:51 am

    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

  • Reply Ian Atkinson August 5, 2017 at 12:05 pm

    I just love Stilton.

  • Reply bandoned_ boy October 5, 2017 at 6:05 pm

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

  • Reply Gojida October 20, 2017 at 8:03 am

    I ate a piece of mochi when I was 10 that had spots of mold. I didn't know what it was but I ate it.

  • Reply Oviraptious October 23, 2017 at 10:55 am

    Food doesnt go bad
    Something just starts eating it before you do

  • Reply Justin _ October 29, 2017 at 4:58 pm

    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.

  • Reply Detective Hip November 8, 2017 at 12:52 am

    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 🙂

  • Reply some random guy on the internet November 22, 2017 at 5:41 am


  • Reply Amira Lozse November 22, 2017 at 10:01 pm

    Hank, you are quite a fungi!

  • Reply Kevin Benoit December 8, 2017 at 7:09 pm

    It’s probably still good… Just gotta scrape the moldy part off and it’s fine to eat.

  • Reply Devantejah December 8, 2017 at 8:12 pm

    If I can feel the mold taste is too strong, then I don't eat it.

    Otherwise it's fair game!

  • Reply Aggie Moon December 11, 2017 at 6:47 am



  • Reply Sergio Alcala December 13, 2017 at 3:40 am

    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

  • Reply iliden strmrege December 14, 2017 at 6:52 am

    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

  • Reply Chloe Chiu December 21, 2017 at 12:55 pm

    great. I just had a pack of molded strawberries.

  • Reply BarneySaysHi December 23, 2017 at 2:02 pm

    I've got the feeling Hank isn't a fan of blue veined cheeses…

  • Reply Random Guy That Comments on Youtube videos December 24, 2017 at 6:40 am

    So if i buy blue cheese im sharing with mold? Damn. I might just buy some blue cheese.

  • Reply Joel Loke December 31, 2017 at 4:34 am

    Do you really have to put the 101???

  • Reply Alisha Gonzalez February 18, 2018 at 11:11 pm

    I kinda want to see less of Hank and more visuals of the videos

  • Reply aidan ! March 25, 2018 at 8:04 am

    I had rotton butter before. I made some toasts but it tasted horrible. I later found mould on the butter

  • Reply Joseph C March 27, 2018 at 4:55 am

    This guy reminds me of the dude from “Good Eats”

  • Reply Jayden Tang Hernandez April 12, 2018 at 8:17 pm

    can eat mold if it's still on the food?????????????????????????????????

  • Reply Nian Factory 4000 Marie April 14, 2018 at 9:44 am


  • Reply GabriellaMZ April 24, 2018 at 10:11 pm

    I'm allergic to penicillin, so does that mean I'm allergic to the mold penicillium roqueforti?

  • Reply Hollowrun May 15, 2018 at 6:41 am

    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

  • Reply Dan_The_Pan _Man May 30, 2018 at 1:34 pm

    Man I my grampa didn't waste anything if he saw mold in bread he said it was just penicillin

  • Reply 100000% Smash June 1, 2018 at 11:17 pm

    I would include dry aged beef in this video

  • Reply YueLin Pua June 25, 2018 at 8:10 am


  • Reply Patrick star fash June 26, 2018 at 6:14 am

    Blue cheese has mold in it gross

  • Reply J.R. Caldoon July 16, 2018 at 9:44 pm

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

  • Reply g g August 1, 2018 at 6:44 am

    2:41 I learned something new today, cheers!

  • Reply Sarah S August 5, 2018 at 9:08 pm


  • Reply 5mnz7fg August 8, 2018 at 7:43 am

    As so often, a deliberately horrible narration. I always wonder why.

  • Reply FishAntsPlantsAndDave August 8, 2018 at 11:24 pm

    Why does this guy put on a fake voice?

  • Reply Larri Capija August 21, 2018 at 1:55 am

    So is blue molded cheese good to eat or not? I’m about to eat it in a salad :v

  • Reply Maddie Jean September 1, 2018 at 12:36 am


  • Reply Hiname HD September 19, 2018 at 4:59 pm

    Can food dye mold

  • Reply prettymochame just T October 21, 2018 at 9:24 pm

    Eat your mold and fungus people, just eat the right ones. Never consume bread with mold.

  • Reply Finalboss711 November 12, 2018 at 4:38 am

    Blue cheese has mold in it.

  • Reply Åñå Türçïøs November 18, 2018 at 2:40 am

    When i see moldy Food i start to throw up

  • Reply Trumble Research November 29, 2018 at 11:23 pm

    I love the sharpest cheese I can find

  • Reply enoch enoch December 12, 2018 at 11:56 am

    Hey one time I eat mold cheese i don't see that already mold is it's for 3 weeks it's danger or no danger

  • Reply qthoshi December 13, 2018 at 12:45 am

    That peach looked really sad.

  • Reply LoanLeaf December 22, 2018 at 12:36 am

    It spreads like mold!

  • Reply videostar75 January 3, 2019 at 5:09 pm

    It digests its food before it eats it…..mind.blown.

  • Reply videostar75 January 3, 2019 at 5:13 pm

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

  • Reply Eilonwy Hewlett February 20, 2019 at 8:45 pm

    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.

  • Reply ReallyOrganic February 23, 2019 at 9:07 pm

    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.

  • Reply Quabledistocficklepo March 1, 2019 at 4:48 pm

    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?

  • Reply CrowSab5 March 22, 2019 at 4:23 pm

    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.

  • Reply Yasmin Bedford April 2, 2019 at 10:18 am

    How does mould affect the texture of foods?

  • Reply that one asian dude April 5, 2019 at 11:13 pm

    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

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