Is Cheese Vegetarian? Rennet, Labels and Alternatives

Most cheese sold in the UK is vegetarian, but a significant minority is not, and some of the world's most famous cheeses never can be. The deciding factor is rennet, the coagulant used to turn milk into curd. If it came from a calf's stomach, the cheese is not vegetarian. If it came from a fungus, a fermentation tank or a thistle, it is.

The confusing part is that nothing on the shelf makes this obvious, the rules differ between the UK and the US, and a cheese can be handmade, organic and artisanal and still contain animal rennet.

What rennet actually is

Rennet is a set of enzymes that make milk set. The important one is chymosin, which snips a specific bond in the kappa-casein protein on the surface of milk's casein micelles. Once that bond is cut the micelles clump together and the milk turns to gel. That gel is curd, and everything else in cheesemaking follows from it.

Traditional rennet comes from the abomasum, the fourth stomach chamber, of an unweaned calf, kid or lamb, which produces plenty of chymosin because it needs to slow milk down in the gut long enough to digest it. The animal has to be slaughtered, which is why animal rennet is not vegetarian.

The four kinds of coagulant

1. Animal rennet

From calves, kids or lambs. Not vegetarian. Still standard in most traditional European cheeses, and mandatory in several protected ones.

A related trap: some Italian cheeses use rennet paste, which contains pregastric lipase from the same animal as well as chymosin, because it produces the sharp, peppery notes in Pecorino Romano and provolone piccante. Animal-derived lipase makes a cheese non-vegetarian even if the rennet was microbial.

2. Microbial rennet

Produced by fermenting certain moulds, principally Rhizomucor miehei, and harvesting the enzymes they secrete. No animal involved, so it is vegetarian. Its weakness is that these enzymes are less specific than chymosin and keep chopping up proteins during ageing, which can leave a faint bitterness in cheeses matured beyond a year. That is why there was for a long time no convincing vegetarian answer to a hard, aged cheese.

3. Fermentation-produced chymosin (FPC)

The clever one, and the reason vegetarian hard cheese got good. The gene for calf chymosin is inserted into a microorganism such as a yeast or a fungus, which is grown in a fermenter and produces chymosin identical to the calf version. The enzyme is purified out, so no modified organism reaches the cheese and no animal is involved.

It was approved for food use in the United States in 1990, one of the first genetically engineered products cleared for the food supply anywhere, and now accounts for most cheese made industrially worldwide. The Vegetarian Society treats it as suitable, and it is what most "vegetarian rennet" on a UK label refers to.

4. Vegetable rennet

Genuine plant coagulants are rare, because most are unpredictable and turn bitter. The one that works is the dried flower of the cardoon thistle, Cynara cardunculus, used in Iberia for centuries. It gives the spoonable, custardy texture of Serra da Estrela and Azeitao in Portugal, and Torta del Casar and Queso de la Serena in Spain. Nettle and fig latex will curdle milk but are not used commercially, whatever the internet says.

The cheeses that are never vegetarian

Protected Designation of Origin status (PDO in the UK and EU, DOP in Italy, AOP in France and Switzerland) locks a cheese's method to a legally binding specification. Where that specification names calf or lamb rennet, no producer can substitute anything else and still sell under that name. There is no vegetarian version, and there will not be while the rules stand. That includes:

• Parmigiano Reggiano DOP. Calf rennet, required by the specification. If it says Parmigiano Reggiano, it contains animal rennet, without exception.
• Grana Padano DOP. Same story.
• Pecorino Romano DOP. Lamb rennet paste.
• Gorgonzola DOP. Calf rennet.
• Gruyere AOP (the Swiss original) and Comte AOP. Calf rennet in both.
• Mozzarella di Bufala Campana DOP. Natural calf rennet.
• Roquefort AOP. Animal rennet.

Two caveats. First, "Parmesan" outside the EU and UK does not always mean Parmigiano Reggiano, so a hard Italian-style cheese labelled Parmesan in an American supermarket may well be vegetarian. Second, these cheeses turn up as ingredients as often as wedges: pesto, Caesar dressing, carbonara sauces and many savoury pastries contain Parmigiano Reggiano or Grana Padano.

PDO status does not automatically mean animal rennet, though. Stilton PDO permits vegetarian coagulants, and Cropwell Bishop makes a vegetarian Blue Stilton.

How to read a label in the UK

There is no legal requirement in the UK to state the source of rennet, which is the root of the problem. What you can rely on:

• "Suitable for vegetarians" is a claim the manufacturer is legally accountable for, so it is trustworthy.
• The Vegetarian Society Approved seal is the strongest signal, because it is independently certified and covers processing aids too.
• "Vegetarian rennet", "microbial rennet" or "non-animal rennet" means what it says.
• "Rennet" with no qualifier should be read as animal rennet.
• Deli counters sell cheese loose, so there is no label. Ask. A good cheesemonger knows the answer for every cheese in the case.

As a rough guide, most British-made supermarket cheddar, Red Leicester, Cheshire, Wensleydale and Cornish Yarg uses vegetarian rennet, because manufacturers switched years ago in response to demand. Continental imports are far more likely to use animal rennet.

How to read a label in the US

Harder, because the conventions are looser.

• "Enzymes" on its own is ambiguous, since FDA rules do not require the source to be named.
• "Microbial enzymes", "microbial rennet", "vegetable rennet" or "non-animal enzymes" are fine.
• "Rennet", "animal rennet" or "calf rennet" are not.
• "Lipase" unqualified is a grey area, since it is commonly animal derived in Italian-style cheeses.
• Certification seals, such as the American Vegetarian Association's, are the quickest shortcut.

When a label says only "enzymes" and there is no seal, the manufacturer's website is the fastest route.

Reliable vegetarian swaps for the classics

• Instead of Parmigiano Reggiano: Twineham Grange from West Sussex is made in an Italian style specifically as a vegetarian alternative, and grates and melts like the real thing. Old Winchester from Lyburn Farm in Hampshire, aged around 18 months, develops the same crunchy tyrosine crystals and nutty depth.
• Instead of Pecorino Romano: a mature vegetarian hard cheese with plenty of salt. You lose the peppery lipase kick, so compensate with black pepper, which is what cacio e pepe rests on anyway.
• Instead of Gorgonzola or Roquefort: vegetarian Blue Stilton, or a creamier British blue in the Stilton style.
• Instead of Gruyere or Comte: a vegetarian mature cheddar for cooking, or a British Alpine-style cheese, since many smaller UK dairies use vegetarian rennet as standard.
• Cheeses that need no rennet at all: paneer, most ricotta, mascarpone and many cream cheeses are set with heat and acid. Ricotta carries an asterisk, since it is made from another cheese's leftover whey, so traces of animal rennet can come along for the ride.

Quick answers

Is Parmesan vegetarian? Parmigiano Reggiano is never vegetarian. Generic "Parmesan" or "Italian hard cheese" made outside Italy often is. Read the label.

Is vegetarian rennet the same as vegan cheese? No. Vegetarian rennet only settles the coagulant question. The cheese is still animal milk, so it is not vegan.

Is FPC or "vegetarian rennet" genetically modified? The microorganism that produces the enzyme is. The enzyme is identical to calf chymosin and no modified organism remains in the cheese. If you avoid anything GM-adjacent, look for microbial or thistle rennet instead.

Is halloumi vegetarian? What about feta? Both are traditionally made with animal rennet and both are now widely available in vegetarian versions. Check the pack, including when you switch brands.

Once you know what to look for it takes three seconds per pack, and the vegetarian options have got dramatically better. Browse the cheese catalogue to find your next one, get ideas from unexpected cheese pairings, and put a good vegetarian hard cheese to work in the ultimate three cheese mac and cheese.

When you find one that stands in for a classic, log it in the cheese tracker so you never work it out twice.