What's in Parmesan cheese that makes it not vegetarian?

November 9, 2025 •

4 min read

The majority of cheeses made in the United States today are actually vegetarian, using non-animal rennet. However, authentic, imported Parmesan, known as Parmigiano-Reggiano, and other traditional European hard cheeses, are distinctly not vegetarian due to a specific ingredient used in their production. The key to understanding what's in Parmesan cheese that makes it not vegetarian lies in the use of animal-derived rennet.

Quick Summary

Authentic Parmesan cheese is not vegetarian because it is made with animal rennet, an enzyme extracted from the stomach lining of young calves. This ingredient is essential for curdling the milk to create the cheese, according to traditional European production methods. While alternatives exist for other cheeses, genuine Parmigiano-Reggiano always uses this animal-based coagulant. Consumers can identify vegetarian-friendly alternatives by checking labels for "microbial rennet," "vegetable rennet," or "vegetarian" certifications.

Key Points

Animal Rennet: Authentic Parmigiano-Reggiano cheese is not vegetarian because it is traditionally made with animal rennet, an enzyme sourced from the stomach lining of young calves.
Protected Designation of Origin (PDO): By EU law, for a cheese to be labeled Parmigiano-Reggiano, it must use animal rennet, a requirement that makes it unsuitable for vegetarians.
Identifying Vegetarian Cheese: Consumers can find vegetarian alternatives by looking for labels that specify "microbial rennet," "vegetable rennet," or explicitly state "suitable for vegetarians".
Common Alternatives: The most common vegetarian substitutes for animal rennet are microbial rennet (from fungi) and fermentation-produced chymosin (FPC), a genetically engineered enzyme.
Soft Cheeses are Generally Vegetarian: Many soft cheeses, such as ricotta, cottage cheese, and cream cheese, do not use rennet and are therefore naturally vegetarian.
Read the Fine Print: When a label simply lists "enzymes," it is often an indication that animal rennet has been used, especially in European or traditional hard cheeses.
Kosher Certification: Kosher-certified cheeses are always vegetarian because Jewish dietary laws prohibit mixing meat and dairy products.

The role of animal rennet in traditional cheesemaking

The ingredient that makes traditional Parmesan cheese unsuitable for vegetarians is animal rennet. Rennet is a complex set of enzymes, with chymosin being the primary component, that cheesemakers use to coagulate milk and separate the solid curds from the liquid whey. This coagulation is a critical step in the cheesemaking process, especially for producing hard, aged cheeses like Parmigiano-Reggiano.

Animal rennet is traditionally sourced from the fourth stomach chamber, or abomasum, of young, unweaned ruminant animals, such as calves, lambs, or goats. Because young mammals rely on milk for nourishment, their stomachs contain a high concentration of the chymosin enzyme needed for digestion. As the animals mature and begin to consume solid food, the chymosin production decreases. The rennet is harvested as a byproduct of the veal industry, meaning the animals are slaughtered to obtain the enzyme.

For a product to be certified as Parmigiano-Reggiano under the European Union's Protected Designation of Origin (PDO) laws, it must adhere to strict traditional requirements, which include using only three approved ingredients: milk, salt, and animal rennet. This legal designation ensures the authenticity and traditional character of the cheese but also guarantees it is not vegetarian.

Vegetarian alternatives to animal rennet

For vegetarians who want to enjoy a Parmesan-style cheese, or any cheese that might traditionally use animal rennet, several alternatives are available. The use of non-animal rennet has become a widespread practice, particularly for mass-produced cheeses in the United States.

Microbial Rennet: Derived from the fermentation of specific fungi or molds, such as Rhizomucor miehei. This is the most common and cost-effective alternative for commercial cheesemaking today. Cheeses made with microbial rennet are suitable for vegetarians and often have a consistent flavor profile, though some experts note minor differences in taste, especially in aged varieties.
Fermentation-Produced Chymosin (FPC): This is a modern, genetically engineered form of rennet. It is made by introducing the animal chymosin gene into microbes, which then produce the enzyme through fermentation. FPC is chemically identical to calf rennet, offering very similar results in texture and flavor, and is widely used by major cheese manufacturers.
Vegetable Rennet: Extracted from plants with milk-coagulating properties, such as artichokes, cardoon thistle, or nettles. This type of rennet is more commonly used in specific traditional cheeses in some Mediterranean regions. It can impart a slightly different flavor profile, sometimes described as herbaceous or even slightly bitter, especially in longer-aged cheeses.

Comparing traditional vs. vegetarian-friendly rennet


Feature	Traditional Animal Rennet	Vegetarian-Friendly Rennet (Microbial/FPC)
Source	Lining of the stomach of young ruminants (e.g., calves)	Fungi, bacteria, or genetically modified microbes
Availability	More common in European cheeses and traditional artisanal cheeses	Widespread in US commercial cheese production
Cost	Typically more expensive due to sourcing	Generally more economical for cheesemakers
Flavor	Contributes to the complex, distinct flavor profiles of traditional aged cheeses	Highly consistent; can have minor flavor differences, especially in long-aged varieties
Ethical Considerations	Not suitable for lacto-vegetarians due to reliance on slaughter	Widely accepted as vegetarian; also suitable for kosher and halal diets
PDO Status	Required for authentic Parmigiano-Reggiano and other PDO-certified cheeses	Cannot be used for cheeses with strict Protected Designation of Origin labels

How to identify a vegetarian cheese

Identifying whether a cheese is vegetarian or not requires careful label reading, as regulations can vary by country and type of product.

Look for specific labels

"Vegetarian" or "Suitable for Vegetarians": This is the most straightforward indication that no animal-derived rennet was used.
"Microbial Rennet," "Vegetable Rennet," or "Plant-based Enzymes": These specific terms confirm the use of a non-animal coagulant.

Understand generic terms

"Enzymes": This is a vague term that could mean either animal or non-animal rennet. If this is the only term listed, especially on a hard cheese, it is best to assume it is not vegetarian unless otherwise specified on the packaging.

Trust certifications

Kosher Certified: Cheese with a Kosher symbol (such as 'K' or 'OU') will not contain animal rennet, as Jewish dietary laws prohibit mixing dairy with meat products.

Other considerations

DOP Status: Avoid products labeled as "Parmigiano-Reggiano," "Grana Padano," or other traditional European hard cheeses with Protected Designation of Origin, as these legally require animal rennet.
Fresh cheeses: Many soft, fresh cheeses like cottage cheese, ricotta, and cream cheese do not use rennet for coagulation. Instead, they use an acid like lemon juice or vinegar.

Conclusion: Choosing your cheese wisely

For vegetarians, the key takeaway is that not all cheese is the same. While the word 'cheese' doesn't explicitly refer to meat, the traditional method for making Parmesan cheese involves an animal byproduct that is non-vegetarian. Thankfully, the modern food industry provides many excellent alternatives that achieve a similar result without using animal rennet. By paying close attention to labels and recognizing key terms like "microbial rennet," vegetarians can make informed choices to align their diet with their ethical standards. For those who enjoy the specific taste and texture of authentic Parmigiano-Reggiano, they may need to explore specialized vegetarian-friendly hard Italian-style cheeses that explicitly state their rennet source.

Exploring vegetarian-friendly Italian-style cheeses

For those seeking a grated, hard cheese alternative, many brands now offer vegetarian versions labeled as "Italian-style hard cheese." These products are intentionally made with microbial or vegetable rennet to be suitable for vegetarian consumption. Brands like BelGioioso and Organic Valley are known to offer vegetarian Parmesan-style options. Some of these vegetarian versions are so well-made that they can be difficult to distinguish from the traditional product in blind taste tests.

Frequently Asked Questions

No, only authentic Parmigiano-Reggiano from Italy and some other traditional European versions are always non-vegetarian. Many Parmesan-style cheeses sold in the United States and elsewhere are made with vegetarian-friendly microbial or vegetable rennet.

Rennet is a complex of enzymes used to coagulate milk in cheesemaking. Animal rennet comes from the stomachs of young ruminants like calves, while vegetarian alternatives are made from microbial (fungi/bacteria) or plant sources.

No, a label that only lists 'enzymes' is ambiguous. To be certain a cheese is vegetarian, look for a label that specifically says 'microbial rennet,' 'vegetable rennet,' or 'suitable for vegetarians'.

Yes, many hard cheese alternatives, often labeled as 'Italian-style hard cheese,' are made specifically for vegetarians using non-animal rennet. Some certified Kosher cheeses are also hard and reliably vegetarian.

Yes, FPC is considered vegetarian. It is made by genetically modifying microorganisms to produce the same enzyme found in animal rennet, but without using any animal byproducts in the process.

Yes, soft cheeses like ricotta, cottage cheese, and cream cheese are typically vegetarian because they are coagulated using an acid, such as vinegar or lemon juice, rather than rennet.

The rennet enzyme is inactivated by high heat, but this does not change the fact that an animal byproduct was used in the cheese's creation. The cheese is non-vegetarian from the moment the rennet is added.