Oftentimes, we think of things getting worse with age. How much money is spent for example on beauty treatments to firm up and smooth out wrinkled skin or on products to restore lost hair. This is true in many cases when we talk about food. Given the choice, most people would prefer a fresh loaf of bread compared to a hard and dried up one from a couple of days before, or recently picked fruit as opposed to fruit harvested many days previously, which is already starting to go bad.

Milk and milk products can though buck this trend. Usually, we think of old milk as being spoilt, but actually if watched over carefully, milk can become something tasty and healthy in the form of sour milk. Beyond this, cheese is perhaps one of the best examples of something that generally speaking improves with age. We could say that there’s no such thing as old cheese, there’s just mature cheese!

The aging ( or maybe more rightly termed maturing process) adds not only flavour to cheese, but it changes it’s consistency and structure, often making it suitable for different uses, such as grating, plus preserving it and concentrating its nutritional value. One particularly interesting example is Casu Marzu, an Italian cheese which is ‚matured’ in a very notable and debatable way.

An Im-pecorino Start

Casu Marzu actually begins life as a different cheese called, “Pecorino Sardo”. Pecora in Italian means sheep and so “Pecorino” is a family of cheese made from sheep’s milk. The “Sardo” refers to “of Sardinia”, in other words, “Pecorino Sardo” is a sheep’s milk cheese from Sardinia.

The Pecorino cheeses can be matured for different lengths of time in order to produce cheeses that range from soft to hard and crumbly. Cheese which has been left for 20 to 60 days forms a thin rind, is straw coloured and has a sweet taste. Alternatively, by leaving the cheese to mature for at least 120 days, a darker rind is formed, the cheese itself becomes straw-coloured and the taste is now strong and slightly spicy.

Whatever the variety, these Pecorino Sardo cheeses are pleasant cheeses with many different uses. One might say that they are impeccable. However, there is a further method that can be used to mature them, producing what is known as Casu Marzu.

A step too far?

Once a nice wheel of Pecorino cheese has been obtained, it would be tempting to think that the cheesemaker’s work is done and now the time has come either to enjoy the cheese himself or to make a little profit by selling it. In Sardinia, though this is not necessarily the case.

At some point in the past it was discovered that by removing part of the rind of the Pecorino cheese and then leaving outside, the cheese becomes infested with small white worms. These are the larvae of the so-called ‘cheese fly’, a little insect that loves to lay its eggs in cheese (not to mention meats and fish). The eggs hatch resulting in the cheese becoming full of the white worms, which begin to eat away at the cheese. Not, you might imagine, the best of situations.

However, as it happens, the worms simply break down the fat in the cheese, causing it to become softer and slightly liquidy. The cheese itself remains edible and in terms of taste, many would say that it is actually improved rathered than harmed in spite of the presence of the little invaders.

Who Would Have Thought of That!

On first hearing, it is hard to believe that people came up with the process for making Casu Marzu, let alone began eating it. With a little meditation though on the subject, a possible explanation is not too difficult.

Perhaps in the past, when fridges weren’t around, some poor peasants in Sardinia found that their last block of Pecorino cheese had become infested by maggots and started to decay. However, due to hunger and poverty preventing them from finding an alternative, they just went for it and ate the cheese anyway.

They were probably pleasantly surprised to find that the cheese still tasted good, arguably better than before, and not suffering any serious ill effects afterwards, decided that in the future a good way to make the most of old Pecorino cheese is to let it decay into Casu Marzu.

A Dangerous Delicacy

Maybe in the past, people consumed Casu Marzu as a result of not having any choice. In this day and age though we are often much more health and hygiene conscience when it comes to our diets.

Because of this, a cheese that contains live worms is probably not everybody’s cup of tea. Indeed, it is debatable if the cheese is even legal due to the fact that it’s production breaks many hygiene rules.

The main health risk of Casu Marzu is that the worms might survive the ingestion process and continue to live in a person’s intestines as parasites. For this reason, the worms can be killed before consuming the cheese either by refrigeration or by sealing the cheese in an airtight bag to starve the worms of oxygen.

Ironically, a sign that the cheese itself is safe to eat is the fact that the worms in it are still alive. If the worms have died naturally, it shows that the cheese has gone too far down the road in the decay process, and so isn’t fit for human consumption anymore

Try it if You Dare!

The very name of this cheese makes it not sound very appetising. ‘Casu’ is a word that means cheese and ‘Marzu’ means rotten or putrid. Arguably, not the first thing that you would want to go for on a restaurant’s menu or to accompany your dinner after a long day’s work.

That being said, in Sardinia at least there is a long tradition of making and eating Casu Marzu, so it can’t be all bad.

Personally, I haven’t tried this cheese and would have to think twice about whether I would if given the opportunity, but for those of us with a strong stomach and an appetite for adventure, it might be worth a go!