Cheese rind: can you eat it? And what to do about mould in the fridge

There are two things we do almost without thinking: cut the rind off cheese before eating it, and throw the whole piece away the moment we spot a patch of mould in the fridge. Our friend Sergio, who looks after sheep and makes the cheeses we sell at Campos del Abuelo, sees this a lot and it makes him sad, because the rind on our cheeses is meant to be eaten and because, in his experience, a cheese with a bit of mould isn't always a lost cause.

But not all rinds are the same. Some are cheese that has turned into a skin over time; others are wax, paraffin or plastic that should never end up in your stomach. And not all moulds are handled the same way: what works for an aged cheese doesn't work for a fresh one.

In this article we explain what sets a natural rind apart from a treated one, why industry seals its cheeses, what mites have to do with all this, what to do when mould shows up at home according to health authorities and according to Sergio's method, and how to store cheese so it stays alive and at its best.

Natural rind: cheese that grows its own skin

Sergio puts it like this:

“Our rind is natural. I make the cheese, put it in salt and it slowly ages. There's nothing added: I don't coat it in wax or paraffin to control the cheese's quality.”

A natural rind is the outer part of the cheese itself. With salt and air, the surface loses moisture, hardens and is colonised by moulds, yeasts and bacteria that are part of the ripening. In soft cheeses, that skin is the Geotrichum that gives them their little wrinkles and works the paste from the outside in (we tell you about it in how our cheeses are born). In an aged cheese like Patamulo, it's a firm, brushed rind that protects the paste during its two or three months of ageing.

The alternative is coating. Royal Decree 1113/2006, Spain's quality standard for cheese, allows the rind of ripened cheeses to be treated with specially prepared waxes, paraffins, polymer materials and mineral oils. And EU rules authorise, only on the surface of hard, semi-hard and semi-soft cheeses, an antifungal called natamycin (E-235), up to a maximum of 1 mg per square decimetre and without reaching deeper than 5 mm. None of these coatings are meant to be eaten.

A note on Comté

Talking about rinds, Sergio mentioned Comté as an exception, which he remembered as being “wrapped in cloth and waxed” because of its long ageing of twelve or eighteen months. His underlying point is right: long ripening calls for different care. But to be precise, the example needs fine-tuning. The specifications for this French designation of origin require a natural rind that is “rubbed, solid and granular”, golden ochre to brown in colour, cared for in the cellar by regular rubbing and salting.

Its minimum ripening is 120 days (four months), the average is around eight, and many are sold at 12, 18 or even 24 months. It's also a cooked pressed cheese, not semi-cooked. Cheeses that really are wrapped in cloth include traditional clothbound cheddars, covered in muslin and lard; and waxed cheeses include Gouda and Edam.

Why industry seals its cheeses

Sergio has a very practical explanation: it's a question of scale.

“I might have a thousand cheeses in the ageing room; they have a hundred thousand in one room. How do they keep an eye on all those cheeses? It's very easy to coat them in wax and paraffin to protect them and stop mites eating them. If the power goes out one day, I can handle it. But them, with a hundred thousand cheeses…”

A natural rind needs constant attention: turning the wheels, brushing them, watching humidity and temperature. With a thousand cheeses, like those in our ageing room, it can be done by hand. With a hundred thousand, any failure, like a voltage drop or a power cut that sends the room's temperature soaring, can ruin a huge batch. Sealing cheese with wax, paraffin or a plastic coating keeps moisture in, prevents unwanted mould and protects it from mites. It's a logical solution at large scale, but it comes at a price: the cheese stops interacting with its environment, and its ripening becomes more uniform and predictable.

Cheese mites

Cheese mites, mainly from the genera Tyrophagus and Acarus, are tiny relatives of spiders that normally live in soil and feed on fungi. In an ageing room, natural rinds covered in mould are a feast for them. In the dairy we link them to damp and heat, and it makes sense: they need humid environments, and a room that warms up speeds up their activity. They look like a fine brown dust on the rind and, if left unchecked, dig little tunnels. Cheesemakers fight them by brushing, vacuuming or blowing the wheels and lowering the temperature.

They're not dangerous to anyone eating cheese in normal amounts. There's even a French cheese, Mimolette, that's deliberately ripened with mites to give it its distinctive rind. In 2013 the US FDA held up its import over excessive mites, and today it's sold there again.

A cheese that breathes

“My cheese breathes. That's what gives it more life. My cheese ages with moulds, which are the natural ferments; in the end it's moulds and yeasts doing the work. It's like a good craft beer.”

The craft beer comparison is spot on. In both cases, yeasts and other microorganisms build the flavour, and every workshop has its own ecosystem. On a natural-rind cheese, the surface is a little forest of moulds, yeasts and bacteria competing for space and nutrients. That community consumes acid, transforms proteins and fats, and produces aromas that a sealed cheese doesn't develop in the same way. It's part of what we mean by a living food.

So, can you eat the rind?

If you're pregnant, or you're giving cheese to young children, older people or anyone immunocompromised, follow AESAN's recommendations on raw milk cheeses, which we go over in is raw milk cheese safe?

Mould in the fridge: should I throw it out?

Sergio hates throwing a cheese away over a bit of mould. As he says:

“It's not for throwing out. The cheese's bacteria protect the cheese itself from other outside moulds and yeasts. With the rind, what I do is brush it and you remove all the mould. And when it appears on the cut face, you scrape it. You scrape it and there's no trace of mould left.”

And he adds something important: you'd have to see where that mould comes from. “If people had a fridge just for cheese, nothing would happen.” A home fridge holds fruit, cured meats, leftovers and bread all together, and spores travel from one to another.

What health authorities say

The Food Safety and Inspection Service of the US Department of Agriculture (USDA), one of the most widely cited references in Spain too, distinguishes three cases:

• Hard and aged cheeses not made with mould: they can be saved by cutting at least 2.5 cm around and below the spot, keeping the knife out of the mould so you don't spread it, then wrapping the cheese in fresh covering. In a dense, dry paste, mould doesn't penetrate far.
• Soft and fresh cheeses (fresh cheese, cream cheese, cottage cheese, ricotta) and any grated or sliced cheese: throw them out. Their moisture lets mould and accompanying bacteria reach deeper without being seen.
• Cheeses made with mould (Camembert, Brie, blues): their own mould is safe, but if a different mould appears on a soft cheese of this type, throw it out; hard ones are treated like aged cheese.

Spanish media specialising in food safety, such as Consumer, give similar advice: with ripe, hard cheeses it's enough to remove the affected outer part, while soft, young cheeses with unexpected mould should be discarded. The reason for so much caution is that some moulds produce mycotoxins, invisible compounds that survive cooking.

Sergio's method, with some nuances

His method fits these recommendations for aged cheeses. Brushing the rind of a cheese like Patamulo when a film of surface mould appears is what's done every day in any ageing room, ours included. When mould appears on the cut face of an aged cheese, his advice to scrape it works if it's just a light fuzz on the surface.

But if the spot is visible and thick, the sensible thing is to follow the health guidance and cut away a generous margin rather than just scraping, because mould filaments can reach a little further than you can see. With soft cheeses, the rule changes: the white mould and wrinkles on Maná and Ambrosía are their rind, but mould of another colour (pink, black, green, or blue on a cheese that isn't a blue), fuzzy or with an odd smell, is a sign it should be thrown out.

A cheese that protects itself like the body

“In the end, cheese is a living system. It's like your body: you cut yourself and your bacteria go there to protect it. Well, cheese does the same.”

It's a lovely image, and science refines it. On a natural-rind cheese, its own microbial community takes up the space and competes with newcomers, just as the microbiota on your skin makes it harder for other microbes to settle. Add to that the acidity, the salt and the low available water in an aged cheese, which keep protecting the paste after it's cut. The nuance is that in your body, what rushes to the wound is mainly the immune system; cheese has no such active defence, so its protection has limits. That's why it works better in a dry aged cheese than in a fresh, moist one.

How to store cheese at home

1. Cold, but not the coldest. Keep it between 4 and 8 °C, ideally in the vegetable drawer, which is the least cold and most humid part of the fridge.
2. Let it breathe. Wrap it in cheese paper or waxed paper and put it in a container with some room to spare. Tight cling film traps moisture and ammonia and encourages unwanted mould.
3. A box just for cheese. It's the home version of the “cheese fridge” we mentioned: keep cheese apart from other foods and, if you can, soft ones apart from aged ones.
4. Protect the cut face with paper wrapped snugly; it's the most exposed part.
5. Buy at your own pace. Better pieces you'll eat within a week or two than big amounts that end up forgotten.
6. Take it out before eating. 30 to 60 minutes at room temperature so it gets its aromas and texture back, and put back only what you won't eat.
7. Check the rind. If a film of mould appears on an aged cheese, brush it off promptly with a clean brush or a dry cloth.
8. Freeze only for cooking. Aged cheeses survive freezing but turn crumbly; use them grated or melted. Soft cheeses lose their texture.
9. Make use of hard rinds from natural cheeses to flavour stocks, soups or stews. Wax or plastic ones go in the bin.

Frequently asked questions

Can you eat the rind of Maná, Ambrosía and Patamulo?

Yes. They're natural rinds, with no wax, paraffin or natamycin. On Maná and Ambrosía, the Geotrichum rind is an essential part of the flavour; on Patamulo, it's a brushed rind you can eat if you like its texture.

What's the brown dust on the rind of an aged cheese?

It may be dried mould or cheese mites, common on natural rinds. They're not dangerous in normal amounts: brush the rind and, if you're not convinced, remove a thin layer.

How much should you cut if mould appears on an aged cheese?

The USDA recommends at least 2.5 cm around and below the spot. If it's just a surface film on the rind, brushing is enough. With soft, fresh, grated or sliced cheeses, throw it out.

Why does my cheese smell of ammonia when I open it?

It happens with soft cheeses with bloomy or washed rinds, especially if they've been wrapped in plastic. Let it breathe for a few minutes. If the smell stays strong and the paste under the rind is slimy or brownish, it's over-ripe.

How can I tell if a rind is wax or plastic?

It's usually smooth, shiny, uniform and coloured red, yellow or black. The label often says “inedible rind” or mentions coatings or natamycin. A natural rind has an irregular texture, moulds and smells of cheese.

A rind you can eat

The cheeses Sergio makes in our dairy ripen with their natural rind, cared for by hand in an ageing room where every wheel can be looked at up close. If you want to try eating a whole cheese, from rind to heart, you'll find Maná, Ambrosía and Patamulo in Reserve your harvest, along with the fruit and veg we pick the same day they ship. From the field to the box, and from the box to your home. That simple, that authentic.

Sources

• USDA FSIS. Molds on food: are they dangerous?
• Consumer (Eroski). Can I eat that cheese? (Spanish)
• Consumer (Eroski). Cheese: its properties and how to store it (Spanish)
• Maldita Ciencia. Mouldy food: what to throw out and what not to (Spanish)
• BOE. Royal Decree 1113/2006, quality standards for cheese and processed cheese (Spanish)
• Polytechnic Institute of Bragança. Conditions of use of natamycin (E-235) in the EU
• EFSA. Scientific Opinion on the use of natamycin (E 235) as a food additive
• INAO. Cahier des charges de l'appellation d'origine «Comté»
• Institut National de la Consommation. Le comté: les secrets d'un fromage jurassien
• Microbial Foods. Microbe guide: cheese mites
• Cheese Scientist. Can you eat cheese rinds?
• Cheese Scientist. Ammoniated cheese