Casu Marzu, sometimes called “the world’s most dangerous cheese”, is one of the most notorious food items on the planet. Originating from the island of Sardinia, this delicacy is infamous not just for its strong flavour but also for its equally bold maturation method.
In this post, we’ll delve into Casu Marzu’s history and its significance to Sardinian culture. Of course, we’ll also dive into the science behind its maturation process, and why it’s been the subject of health and legal debates for years.
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Synonyms
Casu martzu, casu becciu, casu fattittu, casu frazigu, hasu muhidu, formaggio marcio.
Cheese snapshot
- Ingredients: Pecorino cheese made from whole milk of Sardinian sheep, with the addition of rennet, salt, and the presence of Piophila casei larvae inside the cheese.
- Sheep breed: Sardinian.
- Shape: Cylindrical.
- Weight: Varies depending on the type of cheese produced in different areas, typically between 2 and 4 kg.
- Type of paste: Generally creamy and spreadable, but it can be firmer depending on the maturation stage. Ranges in colour from white to straw yellow, with brownish shades.
- Rind: Typically soft to semi-hard, non-uniform with a firmer edge. The colour changes with maturation, ranging from deep yellow to brown or dark brown.
- Flavour and aroma: Has a distinct, intense aroma. It melts in the mouth, leaving a strong taste, often spicy due to the lamb’s rennet. The aroma recalls the scents of Mediterranean scrub.
Origins and history of Casu Marzu
Casu Marzu, which translates from Sardinian as “rotten cheese”, is deeply rooted in the pastoral traditions of Sardinia. This small island south of Italy has a long history of sheep farming and cheesemaking. Sardinia’s shepherds have been producing Pecorino, the base cheese for Casu Marzu, for thousands of years.
Pecorino itself is a firm, savoury cheese made from sheep’s milk. Legend has it that a few centuries ago, a batch of cheese was accidentally contaminated by the larvae of the cheese fly (Piophila casei). Consequently, those wheels of Pecorino naturally began to ferment beyond the usual stages of ageing.
What began as an unintentional event soon became a tradition. Locals noticed that this fermentation process created a softer, more pungent cheese. And would transform the otherwise firm Pecorino into something more creamy, with complex flavours and aromas.
What might have been considered spoiled by some was instead embraced by Sardinian shepherds. Eventually, the cheese earned a special place in Sardinian culture.
Where is Casu Marzu made today?
The production facilities are mainly located on livestock farms, and Casu Marzu production typically takes place in the homes of breeders.
These locations have specific microclimatic conditions, particularly regarding temperature and humidity, which are essential for the fly’s activity. The final product is often stored in cooler environments, sometimes in a refrigerator.
How Casu Marzu is made
Pecorino stage
The making of Casu Marzu starts much like Pecorino cheese production. Fresh sheep’s milk is curdled using natural rennet, after which the curd is pressed and moulded into cheese wheels.
These wheels are then aged for a few weeks, allowing them to develop a firm texture. But what happens next is what distinguishes Casu Marzu from other cheeses.
Larval stage
The uniqueness of this product comes from the presence of the larvae of the Piophila casei (cheese skipper) fly, attracted to the cheese’s scent. During maturation, expert cheesemakers use traditional techniques to help create favourable conditions for the fly to lay eggs.
These measures include reducing the brining time to avoid bacterial fermentation while still attracting the insect. The cheeses are lightly pressed, and sometimes small holes are made in the rind with a few drops of oil to soften the rind and attract the fly.
In addition to this, limited handling of the cheeses also helps. Once larvae are detected, the affected cheeses are separated and stored in a controlled environment. To promote further larval development, the cheese paste may be broken up inside the cheese. Finally, some makers stack their cheese wheels, allowing the larvae to pass from one to another.
Since the Piophila casei population is highly sensitive to temperature, climatic conditions are critical. As a result, its production is seasonal, from late spring to late autumn, depending on the weather.
Once the larvae are detected, the cheese is cut on one side to create a lid (called su tappu) to monitor the fermentation process.
The science behind Casu Marzu
Undoubtedly, the process of allowing cheese to decompose with the help of live larvae is fascinating from a biochemical perspective.
The larvae of cheese skipper fly excrete enzymes that accelerate the breakdown of fats and proteins in the cheese, resulting in a soft, spreadable texture. This chemical reaction also creates a range of volatile compounds responsible for the cheese’s intense aroma and complex flavours.
Health risks associated with Casu Marzu consumption
However, the very thing that makes Casu Marzu so unique has also made it a topic of scientific scrutiny. Indeed, there are legitimate safety concerns when consuming food that’s essentially in an advanced state of decomposition.
The larvae, although generally safe to eat, can potentially survive in the human digestive system, leading to a condition known as intestinal pseudomyiasis. While rare, it is a potential health risk.
Symptoms of intestinal pseudomyasis
- Abdominal pain: Patients may experience cramping or discomfort in the abdominal area.
- Nausea and vomiting: The presence of larvae can cause digestive disturbances, leading to nausea and sometimes vomiting.
- Diarrhoea: Infestation can lead to gastrointestinal upset, resulting in diarrhoea.
- Anal itching: In some cases, larvae can exit the body through the anus, causing itching and irritation in the rectal area.
- Weight loss: Prolonged infestation may lead to malnutrition and weight loss.
Intestinal pseuomyiasis can be a serious condition if not addressed promptly, so seeking medical attention if symptoms arise is crucial.
Bacterial infections
Beyond the risk of larval infection, there’s also the broader issue of bacterial contamination. Since Casu Marzu is a raw milk cheese, and it undergoes a process of natural fermentation with minimal control over the conditions, it can be vulnerable to harmful bacteria like Salmonella or E. coli.
Taste, aroma and texture of Casu Marzu
The taste of Casu Marzu is powerful and complex. It’s creamy, with a strong, earthy flavour and a slightly spicy kick. The texture can range from soft to almost liquid, depending on the duration of fermentation.
While the ammonia-like aroma can be off-putting to some, those who appreciate bold flavours find it to be part of the appeal.
The experience of eating Casu Marzu
For those brave enough to try it, eating Casu Marzu is an unforgettable experience.
When the cheese becomes creamy, it is consumed by lifting the lid and scooping out the paste with a spoon. While the larvae contribute to this unique texture and taste, they also remain very much alive when the cheese is consumed.
In fact, the presence of live larvae is often seen as a sign that the cheese is fresh. It’s common to find the larvae wriggling around the surface, and in some cases, people report that they can leap as high as 15 cm (6 inches) when disturbed!
Locals often serve this cheese with traditional Sardinian flatbread called pane carasau and a glass of strong red wine like Cannonau. Some people choose to remove the larvae before eating the cheese, while others consume them as part of the experience.
Those who do not wish to eat them place the cheese in a sealed paper bag. The larvae, starved for oxygen, writhe and jump in the bag, creating a “pitter-patter” sound. When the sounds subside, the larvae are dead and the cheese can be eaten.
Cultural significance of Casu Marzu in Sardinia
For many Sardinians, Casu Marzu is more than just a cheese; it’s a symbol of heritage, community and the island’s agricultural roots. The cheese is often eaten at special occasions like weddings, festivals and family gatherings.
Because of the cheese’s controversial nature, it has faced significant pushback from food safety regulators both in Italy and across the European Union. For years, it was illegal to sell due to health concerns associated with consuming food infested by live larvae.
However, Casu Marzu never disappeared. Sardinians continued to produce and eat the cheese as part of their culinary identity, often sharing it only with close friends and family to avoid legal repercussions.
In 2004, after much lobbying, Sardinians succeeded in getting Casu Marzu declared a Prodotto Tradizionale della Sardegna (traditional Sardinian food product). This designation provides protection for foods that are tied to regional heritage, allowing them to be made and sold locally without interference from broader health regulations.
The future of Casu Marzu
In an era where pasteurisation, food safety regulations and mass production have taken over much of the food industry, Casu Marzu is a reminder that some things cannot be replicated in a factory.
However, Casu Marzu’s future remains uncertain. While it has been granted protection as a traditional food, it’s still produced on a very small scale, and the legal gray areas surrounding its production and sale make it impossible to find outside of Sardinia.
Moreover, as younger generations of Sardinians are increasingly exposed to globalised food culture, the question of whether Casu Marzu will continue to be cherished or fade into obscurity remains open.
Conclusion
Casu Marzu is much more than a strange cheese with a shocking reputation. It’s a window into the history, culture, and traditions of Sardinia. And a testament to human ingenuity and the complex relationship between food, science and society.
Whether you’re fascinated or repulsed by the idea of eating cheese filled with live maggots, there’s no denying that Casu Marzu sparks curiosity.
In the end, Casu Marzu challenges us to rethink our relationship with food, culture and the natural processes that make both possible. While it may not be for everyone, for those who embrace it, Casu Marzu is a unique and irreplaceable part of Sardinian lore.
Have you tried this unique cheese? I’d love to hear about your experience in the comments below.
Jonah is a a hipster, eco-warrior and slow food afficionado. Coming from a scientific background, Jonah has a particular interest in cheese science. And yes, he loves a good cheese pun!
