The rule that settles it
Genuine Parmigiano Reggiano is never vegetarian. That is not a matter of interpretation — it is written into the cheese's PDO (Protected Designation of Origin) rules, which specify calf rennet as a required ingredient. The same applies to Grana Padano and Gorgonzola. If a cheese carries one of those names, it was made to a protected specification, and that specification demands an animal product.
For anyone cooking for a vegetarian guest, or eating as one themselves, this is worth knowing clearly rather than assuming. The cheeses are not almost vegetarian, or vegetarian depending on the producer. They cannot be, by definition.
What rennet actually does
Rennet is the enzyme that causes milk to set into curd. Without it — or something that performs the same function — you do not have cheese in any recognisable sense. Traditionally, rennet came from the stomach lining of young ruminants, calves in particular, where it occurs naturally to help digest milk. Cheesemakers have relied on this for centuries, and for certain protected cheeses, nothing else is permitted.
The critical enzyme within rennet is called chymosin. It is what does the actual work of coagulation, and it is chymosin that modern alternatives seek to replicate.
Vegetarian rennet, and how it works
Most cheese made in Britain today — including the vast majority of cheddar, brie-style, and hard cheeses from independent dairies — uses one of two vegetarian alternatives.
- Microbial rennet is derived from certain moulds. It sets milk effectively, though some cheesemakers find it can introduce a faint bitterness in long-aged cheeses.
- Fermentation-produced chymosin (FPC) is the more widely used option. It is the identical enzyme to calf chymosin, produced by fermenting a microorganism that carries the relevant gene. The result is molecularly indistinguishable from the animal-derived version, but no calf is involved in producing it.
Neither of these is a compromise in terms of cheesemaking quality. FPC in particular is now the default across much of the British cheese industry, including many large-scale and farmhouse producers alike.
Reading the label correctly
The phrase to look for is 'suitable for vegetarians'. On British-made cheese, this is a reliable signal that no animal rennet was used. It is not always printed prominently, but it is almost always there if it applies — on the rind label, the wrapper, or the retailer's product description.
What the label will not tell you is which vegetarian rennet was used. That distinction matters little to most shoppers, but if you are curious, smaller independent producers are usually happy to say. Many are proud of the choice they have made.
Imported European cheeses with PDO status are a different matter. The protected rules for Parmigiano Reggiano, Grana Padano, and Gorgonzola do not permit vegetarian rennet, so no version of those specific cheeses — wherever you buy them — will carry that label. A wedge claiming to be Parmigiano Reggiano while also being suitable for vegetarians is a contradiction: one of those claims would be wrong.
The practical workaround
British cheesemakers produce excellent hard cheeses made with vegetarian rennet that perform well wherever you might reach for Parmesan — finely grated over pasta, stirred into risotto, or eaten in shards with a glass of something dry. They do not carry the protected name, and they are not identical to the Italian original, but several are aged to a comparable depth of flavour. Seeking them out is less a concession than a discovery.
The simplest approach at the cheese counter or online is to state plainly what you need: a hard, aged cheese, suitable for vegetarians. Any decent cheesemonger will know exactly what to point you towards.
