I visit Sardinia almost every year since I was a teenager, and I've eaten casu martzu many times. Once you get past the maggots (which I hate) it's actually a very good pecorino cheese (my favourite is Roman pecorino cheese, but being from Rome I am biased)
It's illegal because it is considered potentially dangerous, but its dangerousness has never been proved, of course it's safer to simply prohibit it, it's quite popular in Sardinia, but not many even on the island eat it and in Sardinia people keep making it anyway, so I think it was the right decision.
Someone feeling sick after eating it in France would be very bad PR for such a small, local, traditional food.
I know of people that went to Sardinia only to taste it, exporting it doesn't make much sense both economically and beaurocracy wise.
As someone born and raised in Sardinia I have never eaten it and I hope I never will ( but other Sardinian chesses are quite good indeed). Of all my friends, I think only one has ever eaten it, mostly as a dare.
Sometimes I think they keep making it just for the tourists.
What is it with Sardinia and weird cheeses btw? Su Callu is another one that I don't really have any interest in trying, at least this description makes it sound....super unappealing.
And it's anything but weird. It's likely that this is how cheese was originally discovered: in the fourth stomach (the abomasum, the "true stomach") of an unweaned ruminant slaughtered for food.
The stomachs of unweaned ruminants are also the traditional source of rennet ("callu" means rennet and callu de cabreddu doubles as rennet). Why unweaned ruminants? Rennet is made of two proteolytic enzymes, chymosin and pepsin, that break apart milk proteins (specifically, caseins) by hydrolysis and cause them to coagulate and turn milk into curd. Chymosin has the strongest clotting power whereas pepsin has the strongest proteolytic power. Stronger proteolysis breaks proteins down into smaller peptides and amino acids and it turns out that those register to our sense of taste as bitterness.
Chymosin has strong clotting power at a pH of 6.2 to 6.4, close to that of fresh milk (around 6.8), whereas pepsin clots milk best at a pH of 1.7 to 2.3 which is way too acidic for cheese and basically impossible to get with the usual way to acidify milk for cheesemaking, fermentation of lactose by Lactic Acid Bacteria. LAB generally don't develop at a pH below 4.6 so I don't think milk can even get to the ideal pH for pepsin just from fermentation (pepsin is probably fine-tuned for the very acidic environment of a mammal's stomach).
So basically, to get the same clotting power with pepsin as with chymosin one would have to make a cheese so tangy and bitter that it would be inedible, if it could even be made in the first place.
Now, the age thing. Both chymosin and pepsin are produced in the stomachs of ruminants, young and old, but younger animals produce more chymosin while older animals produce more pepsin. I think it's something like 75/25% chymosin/pepsin for unweaned animals and the opposite for adults, I don't remember. So, to have maximum milk clotting power with slower proteolysis, and less chance of developing bitter tastes, you need to use the rennet from a young animal, preferrably one that hasn't yet eaten grass. It appears that eating grass is what triggers the mechanisms that start producing more pepsin than chymosin. Don't ask me why because I have no idea.
This is an awesome comment.
As I said in a comment below su caggiu (or callu, it depends from where you are, we sardinians have a dialect for each village) is my preferred cheese, now I know more than before about it, thanks.
I knew that, my issue with it is that normally you use a single calf stomach to make loads of cheese. Here you slaughter a calf and hang the stomach to dry and ferment for months to produce a single(not very large) amount of cheese. Just seems wasteful.
It's illegal because it is considered potentially dangerous, but its dangerousness has never been proved, of course it's safer to simply prohibit it, it's quite popular in Sardinia, but not many even on the island eat it and in Sardinia people keep making it anyway, so I think it was the right decision.
Someone feeling sick after eating it in France would be very bad PR for such a small, local, traditional food.
I know of people that went to Sardinia only to taste it, exporting it doesn't make much sense both economically and beaurocracy wise.