Patrick Oconnell
Swiss cheese is known for its distinctive holes, often called eyes, which range in size from small to large and contribute to the cheese's mouthwatering, slightly nutty taste and light, airy feel. While it was once believed that these holes were caused by carbon dioxide released by bacteria, it is now thought that they are caused by tiny bits of hay present in the milk, which create weaknesses in the structure of the curd, allowing gas to form and create the holes. However, this discussion of Swiss cheese's holes may leave some people wondering if the cheese is made with worms. In fact, while there is a type of cheese made with live insect larvae, or maggots, known as casu martzu, it is not Swiss cheese but rather a traditional Sardinian sheep milk cheese derived from pecorino.
| Characteristics | Values |
|---|---|
| Holes in Swiss cheese | Caused by carbon dioxide released by bacteria present in the milk |
| Caused by tiny bits of hay present in the milk | |
| Caused by microbes | |
| Caused by a particular bacterial strain known as Propionibacterium | |
| Varieties without holes | Known as "blind" |
| Varieties with holes | Emmental and Gruyère |
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What You'll Learn
- Swiss cheese holes are caused by bacteria and carbon dioxide
- Casu martzu, Sardinian cheese with worms, is considered unsafe to eat when the maggots have died
- European Union food regulations have outlawed Casu martzu, but it is still produced and sold on the black market
- Variations of Casu martzu are produced in other Italian regions, such as Puglia and Calabria
- Similar cheeses modified by mites, not larvae, are produced in Germany and France
Swiss cheese holes are caused by bacteria and carbon dioxide
Swiss cheese is known for its distinctive holes, often called "eyes". The holes are not just a quirk of appearance but also contribute to the cheese's mouthwatering, slightly nutty taste and light, airy feel. But what causes these holes?
The answer lies in the cheese-making process and the role of microbes. Bacteria cultures are essential in making cheese. They consume lactic acid in the cheese and produce carbon dioxide gas as a byproduct. This gas doesn't disappear but instead forms air pockets within the cheese, creating the holes that give Swiss cheese its unique appearance and texture.
The primary bacteria responsible for these holes are a strain known as Propionibacterium. These microscopic, gram-positive, non-motile bacteria specifically transform the lactic acid into carbon dioxide. This process was first explained by William Clark in 1917, and his idea was widely accepted for almost a century.
However, in 2015, a study by Agroscope, a Swiss agricultural institute, challenged Clark's theory. Agroscope researchers proposed that the holes were caused by tiny bits of hay present in the milk. They suggested that when cheese is made in barns using open buckets, hay particles can contaminate the milk and create weaknesses in the curd structure, allowing gas to form and create the holes. This theory explains why the holes have become smaller or even nonexistent in modern times, as cheese-making practices have evolved.
So, while the bacteria and carbon dioxide play a crucial role in forming the holes, the presence or absence of hay particles can also influence the size and occurrence of the eyes in Swiss cheese.
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Casu martzu, Sardinian cheese with worms, is considered unsafe to eat when the maggots have died
Swiss cheese is known for its distinctive holes, but it is not made with worms. The holes, or "eyes", are caused by carbon dioxide released by bacteria during the cheese-making process, as well as tiny bits of hay that find their way into the milk.
However, there is a type of cheese made with worms, or rather, insect larvae. Casu martzu, also known as casu marzu, is a traditional Sardinian sheep milk cheese that is deliberately made with live insect larvae, specifically the larvae of the cheese fly Piophila casei. The female P. casei lays her eggs in the cheese, and when the eggs hatch, the resulting maggots break down the cheese's fats with their digestive acids, creating a very soft texture.
The consumption of casu martzu is considered unsafe when the maggots in the cheese have died. Therefore, it is traditionally eaten when the maggots are still alive, although some people choose to avoid ingesting them. Those who do not wish to eat the maggots may place the cheese in a sealed paper bag, causing the maggots to writhe and jump until they eventually die from lack of oxygen. Only then will they consume the cheese.
The traditional way of consuming casu martzu involves cutting the cheese into thin strips and spreading them on moistened Sardinian flatbread (pane carasau), often served with a strong red wine like cannonau. The cheese is considered an icon of Sardinian pastoral culture and is even believed by locals to be an aphrodisiac. However, due to European Union food hygiene regulations, the production and sale of casu martzu have been outlawed, with offenders facing heavy fines. Despite this, some Sardinians continue to produce and consume the cheese, and it is available on the black market.
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European Union food regulations have outlawed Casu martzu, but it is still produced and sold on the black market
Casu martzu, also known as the "forbidden cheese" or "maggot cheese", is a traditional Sardinian delicacy. It is derived from pecorino, a sheep milk cheese, and is known for containing live insect larvae or maggots. The process of making this cheese involves deliberately introducing the larvae of the cheese fly Piophila casei to the cheese, allowing them to grow and promoting an advanced level of fermentation. The acid from the maggots' digestive system breaks down the cheese's fats, resulting in a very soft texture and a strong flavour.
Due to the potential health risks associated with consuming Casu martzu, it has been banned in Italy and prohibited across the European Union due to food safety regulations. The larvae can survive the acidic environment of the stomach and remain in the intestine, leading to a condition called pseudomyiasis, which can cause abdominal pain, nausea, vomiting, and bloody diarrhoea. Additionally, the larvae may carry harmful microorganisms that increase the risk of infections. Offenders who sell the cheese can face hefty fines of up to €50,000 (approximately $60,000).
Despite the ban, Casu martzu is still produced and consumed in Sardinia, where it is considered a traditional food. Some Sardinians have organised to make it available on the black market, and the cheese may be sold for double the price of ordinary pecorino. The illegal production of this cheese was estimated at 100 tonnes per year as of 2019, worth between €2–3 million. Attempts have been made to have the ban lifted by declaring Casu martzu a traditional food.
The overall fermentation process of Casu martzu takes approximately three months. It is considered unsafe to eat when the maggots in the cheese have died, so only cheese with live maggots is typically consumed. Some consumers who do not wish to ingest the maggots place the cheese in a sealed paper bag, causing the maggots to writhe and jump due to oxygen deprivation. When the sounds subside, indicating the maggots are dead, the cheese can be eaten.
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Variations of Casu martzu are produced in other Italian regions, such as Puglia and Calabria
Casu martzu, also known as the Sardinian sheep milk cheese, is considered unsafe to eat when the maggots in the cheese have died. It is produced by leaving whole pecorino cheeses outside with part of the rind removed, allowing female cheese flies (Piophila casei) to lay their eggs in the cheese. These eggs hatch into larvae, which feed on the cheese, breaking down its fats and softening its texture. The larvae themselves are consumed along with the cheese and are believed to sometimes survive the stomach acid, remaining in the intestine and potentially causing infections.
While Casu martzu is traditionally associated with Sardinia, variations of this cheese are produced in other Italian regions, such as Puglia and Calabria. In these regions, the process of creating cheese with fly larvae is similar to that of Casu martzu. The main difference lies in the type of milk used and the specific techniques employed during the cheese-making process.
In Puglia, for example, local cheesemakers may use a combination of sheep's and goat's milk to create a variation of Casu martzu. They follow similar steps of leaving the cheese exposed to attract the cheese flies and facilitate egg-laying. However, they might incorporate additional ingredients or aging processes to impart a unique flavour and texture to their cheese.
Calabrian cheesemakers, on the other hand, are known for their traditional methods and the use of local ingredients. Their variation of Casu martzu might incorporate herbs or spices native to the region, adding a distinct flavour profile to the cheese. The specific climate and environmental conditions of Calabria can also influence the aging process and the behaviour of the larvae, resulting in subtle differences in the final product.
These regional variations of Casu martzu showcase the creativity and ingenuity of Italian cheesemakers, who have adapted the traditional Sardinian cheese-making process to their local resources and traditions. While the fundamental aspect of introducing fly larvae remains consistent, each region imparts its unique touch, resulting in diverse flavours, textures, and characteristics of the final cheese product.
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Similar cheeses modified by mites, not larvae, are produced in Germany and France
Swiss cheese is dotted with holes, also called "eyes", and varieties without these holes are known as "blind". The eyes are caused by tiny bits of hay present in the milk, according to researchers at the Swiss agricultural institute, Agroscope.
While Swiss cheese does not contain worms or larvae, similar cheeses modified by mites, not larvae, are produced in Germany and France. These include Milbenkäse, Cantal, and Mimolette. Mimolette, produced in Lille, France, is known for its textured crust, which is caused by Acarus siro mites, also known as flour mites. These mites are intentionally placed on the cheese's surface, contributing to its flavour and giving it a distinctive appearance and grey colour. The mites bore into the cheese's crust, moving towards the softer centre, and leaving behind a floral, sweet flavour.
Mites are present in all different types of dry goods, like grains and flours, without causing direct harm to humans. They are especially prevalent in the damp, cool atmosphere found in the cave d’affinage, or cheese-aging chamber. Mites tend to be present on the outside of hard cheeses, such as Cheddar and Mimolette, and can usually be brushed off the rind without affecting the flavour. However, in the case of Mimolette, the mites are intentionally used to enhance the flavour and appearance of the cheese.
Cheese mites are microorganisms that look like fine brownish dust. They can render a cheese inedible if left to their own devices, as they will take over a piece of cheese. However, when intentionally used in cheese-making, they can be beneficial, contributing to the flavour and texture of the cheese.
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Frequently asked questions
No, Swiss cheese is not made with worms. The holes in Swiss cheese are caused by carbon dioxide released by bacteria present in the milk.
Casu martzu, also known as casu marzu, is a traditional Sardinian sheep milk cheese that contains live insect larvae, commonly referred to as maggots.
Casu martzu is made by leaving whole pecorino cheeses outside with part of the rind removed, allowing female cheese flies to lay their eggs in the cheese. The eggs hatch and the resulting larvae break down the cheese's fats, creating a very soft texture.
Casu martzu is considered unsafe to eat by some when the maggots in the cheese have died. Therefore, only cheese in which the maggots are still alive is usually eaten. However, it is important to note that this cheese has been outlawed due to European Union food hygiene-health regulations.
Yes, there are several other examples of cheeses made with insects or their larvae. For instance, in Puglia, there is frmag punt, a cheese with holes made by a pointed instrument to let the flies in. In Abruzzo, Italy, there is a cheese called cacio marcetto, which is similar to casu martzu. In Germany, there is a cheese called milbenkase, which is modified by mites, and in France, there is a similar cheese called mimolette.
