Monday, August 13, 2007

Myths About Moldy Cheese

Cheese Myth #957: "If there is only a small amount of visible mold on a cheese, it can always be scraped off and the remaining cheese salvaged."

Some supporters of this myth think that cheese cannot be ruined by mold because in some sense cheese is mold or at least is derived from mold. While it is true that molds are often used in cheesemaking, it is not a necessary ingredient.

Cheese is simply what you get by isolating the solid material in milk. Separating the curds (the solid part of milk) from the whey (the liquid part) most often begins with the addition of a starter culture to fresh milk. Starter culture is always a kind of bacteria, whereas mold is a kind of fungus. I think Myth #957 gains some of its support from the conflation of mold with bacteria.

In any case, starter bacteria is not even strictly necessary to cheesemaking. Its primary role is to increase the acidity of milk, so that the separation of curds and whey happens more quickly. Some quick and easy cheesemaking recipes bypass the starter culture and call for adding lemon juice to fresh milk to increase its acidity. This doesn't result in the best cheese, but it illustrates how starter bacteria is not absolutely essential to the process.

After curds are isolated from the milk, you've got cheese. The curds they can be cut, pressed or enriched with various additional flavors without molds ever entering the picture.

Molds do play an important role in the production of blue cheeses and soft-ripened cheeses like Brie and Camembert. Penicillium roqueforti, for example, is used in the production of Roquefort and other blue cheeses, and Penicillium camemberti and Penicillium candida are used in Brie and Camembert. (A different variety of Penicillium is used to produce penicillin.) Most types of cheese, however, do not require the action of any kind of mold.

In my early days as a cheese taster, I made the mistake of buying some blue cheese from an ordinary grocery store instead of from a specialty cheese retailer or an upscale grocer. Unsurprisingly, the cheese was nasty. Who knows how long it had been languishing in the display case. When I returned the cheese to the store, one of the workers was reluctant to give me my money back for the following reason: I complained that a blue cheese smelled and appeared nasty, but blue cheese is supposed to smell and appear nasty.

The grocery clerk's mistake lies in thinking that any kind of nastiness is appropriate in a blue cheese because allowing the cheese to mold is an essential part of its production. The fact is, however, that only a carefully selected strand of mold was introduced into the cheese--and this under closely monitored conditions. It is not the case that any old mold will do.

Some think of the growth of mold on cheese as a kind of controlled spoilage. One should not forget, however, that it is controlled rather than indiscriminate spoilage. Cheese Myth #957 fails to separate controlled spoilage from spoilage due to incorrect storage, refrigerator mold, bacteria or other foreign pathogens.

I don't think the 'controlled spoilage' motif is a very good one because 'spoilage' wrongly suggests destruction. The biochemical processes involved in mold growth on cheese, however, are productive. Baker's yeast (another kind of fungus) doesn't spoil flour and oil. It makes certain kinds of bread possible. Do the yeasts that turn grape juice into wine "spoil" the grape juice? Not if your intent is to make wine. In that case, it's an important part of the production process.

If you find a small amount of mold growing on a hard cheese (e.g., Cheddar, Parmesan), you can generally scrape it off and the cheese will be OK to eat. To some extent, then, there is a grain of truth in Myth #957. Unwanted mold on soft cheeses, however, is more of a problem. One reason is that the molds can more easily penetrate into the heart of soft cheeses than they can into harder cheeses. This causes spoilage from within that cannot be scraped away.

When buying soft or blue cheeses, there are several things you should look for. First, look for grey or pink discoloration around the edges. Fresh, unspoiled cheeses never display these colors. Also, look to see how many wedges of the cheese you want to buy are in the display case. Never buy one of the last wedges of a cheese round. In ordinary grocery stores, blue cheeses do not sell quickly. In fact, even at Premier Gourmet, where I buy most of my cheeses, the blue cheeses move rather slowly. In such a store, the last wedge of a blue cheese will likely be spoiled before anyone buys it. One nice feature of Wegman's grocery stores is that they put the date a wedge is cut on the label of the cheese.

Don't be afraid to ask the person behind the cheese counter to cut you a new wedge of cheese, even if several can be found in the display case. Also, feel free to ask them to remove an unwanted outside portion of a cheese round if it doesn't look like something you want to eat.

Finally, if you didn't already think America had enough pointless holidays, here is one more: October 9th is officially Moldy Cheese Day.


  1. :) did you know how cheese was invented? It wasnt necessity, it was an accident, read this

  2. Thank you for a very informative article.

    I was told that the mold on cheese was penicillin and a person could eat it. That it was healthy to eat.

    So ,I've mostly cut it off and eaten the cheese. I must admit that I've eaten a little of the white mold on cheese before. I've grated the cheese firstly .

    I do not recall becoming ill from eating it.

    But have thrown away moldy soft cheese

  3. The blue in blue cheese and the white, fuzzy layer on the outside of Brie or Camembert are Penicillium molds. 'Penicillium' is the name for a genus of fungi. The stuff growing on the outside of old cheese may or may not be ones of these varieties of fungi.

    The white and blue molds used in cheesemaking do not belong to the same species as that used to make penicillin. So, you can't innoculate yourself against disease by eating old cheese.

  4. Hello,

    I ate cheese with a bit of moldy green/white fuzzy growth, and only realized after eating it. I know it seems like I am stupid, but it was really unnoticeable the first time. Am I going to get sick, is there anything I should do. Please let me know. Thank you.

  5. Deepti, you have nothing to worry about.

  6. Once I scarfed down a whole pizza that tasted like bleu cheese, and realized later that it was super moldy. My instinct was to start to gag, thinking I would sick, but it was all in my head- I was totally fine, and nothing happened. Won't do that again though!

  7. It was extremely interesting for me to read the blog. Thanx for it. I like such topics and everything connected to them. I would like to read more soon.

  8. Thanks for this article. I absolutely love stinky blue cheeses, but was curious as to why these molds were unique.Very informative!

  9. Hi,
    I had to do a Biology homework assignment where I had to find different cheeses (cheese's?) and their bacteria for ten different ones. Your blog REALLY helped me fill out a few. Thanks a lot!

    (PS, No matter what anyone says, I am still not eating blue cheese :D )

  10. James, thank you for the information. One more bit of information I was looking for is the proper 'etiquette' for eating the mold on the exterior of cheese such as Brie or Camembert. I have always enjoyed the pungent taste, but some people are put off by watching me eat it. They are convinced that it must be removed before eating.

  11. Hi! I'm doing a science project on moldy cheese and this site really helped! thank you so much for thinking of this subject! it helped with my research

  12. Thanks for the info. I'm allergic to penicillin so knowing this really helps. :)


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