Decoding the Label: Why isn't mozzarella vegetarian? The truth about rennet

November 9, 2025 •

3 min read

A surprising number of vegetarians have mistakenly consumed cheese made with animal-derived ingredients. The truth behind the question, 'Why isn't mozzarella vegetarian?', lies in a traditional cheesemaking enzyme called rennet.

Quick Summary

Traditional mozzarella is often not vegetarian due to the use of animal rennet for milk coagulation. However, many modern and mass-produced versions utilize vegetarian-friendly microbial enzymes instead.

Key Points

Rennet is the determining factor: Traditional mozzarella is not vegetarian because it uses animal rennet, an enzyme from the stomachs of young ruminants.
Microbial rennet is the vegetarian alternative: Many modern mozzarellas use microbial enzymes sourced from fungi or bacteria, making them vegetarian-friendly.
Check the label carefully: Always look for "microbial enzymes" or "vegetarian rennet" on the ingredients list, as labels can be vague.
Not all mozzarella is the same: Traditional Italian varieties, especially those with PDO labels, are more likely to contain animal rennet, while mass-produced versions are often vegetarian.
Kosher cheese is vegetarian: If a cheese is certified kosher, it will be made with non-animal rennet.
Fresh cheeses can be made with acid: Certain fresh cheeses, including some mozzarellas, can be made using acid instead of rennet, providing another reliably vegetarian option.

The Surprising Non-Vegetarian Ingredient

For many, mozzarella is a staple—the quintessential cheese for pizza, caprese salads, and countless Italian dishes. As a dairy product, it appears to be perfectly suitable for a lacto-vegetarian diet. However, for a long time, traditional mozzarella was often off-limits to strict vegetarians. The key to understanding why lies in the production process and a specific enzyme: rennet. Traditional animal rennet is sourced from the stomach lining of young ruminant animals, most commonly calves. This critical ingredient, which helps curdle the milk and separate the curds from the whey, means that many traditional European cheeses, including certain mozzarellas, are not vegetarian.

The Role of Rennet in Cheesemaking

Rennet is a complex of enzymes, primarily chymosin, that plays a crucial role in cheesemaking. Its job is to coagulate the casein proteins in milk, turning the liquid into solid curds and liquid whey. Without a coagulating agent, milk would not form the solid texture required for cheese production.

In traditional cheesemaking, especially for specific protected Italian cheeses like Parmigiano-Reggiano, the use of animal rennet is a legal requirement. The enzymes help develop the characteristic flavor and texture associated with these aged cheeses. The source of this animal rennet, derived from the stomach of a slaughtered calf, is why many vegetarians avoid it, as it is a byproduct of the meat industry.

The Rise of Vegetarian Alternatives

Thankfully for cheese-loving vegetarians, modern food science has provided a variety of non-animal rennet options. The most common vegetarian alternative is microbial rennet, which is derived from specific fungi or bacteria. This type of coagulant is now widely used, especially in mass-produced and fresh cheeses, as it is cost-effective and doesn't carry the ethical concerns of its animal-based counterpart. Another popular alternative is Fermentation-Produced Chymosin (FPC), a genetically engineered version of chymosin that is molecularly identical to the calf-derived enzyme but produced without any animal inputs.

In some cases, especially with fresh cheeses like mozzarella, ricotta, and paneer, coagulation can even be achieved through direct acidification, using an acid like citric acid or vinegar instead of rennet altogether. This process is faster and makes these cheeses more reliably vegetarian.

How to Identify Vegetarian-Friendly Mozzarella

To ensure your mozzarella is vegetarian, checking the label is essential. However, the terminology can sometimes be vague.

Here’s what to look for:

Vegetarian-Friendly Labels: Look for explicit labels that state “vegetarian,” “vegetarian rennet,” or “microbial enzymes”.
Kosher Certification: Kosher cheeses are reliably vegetarian, as rabbinical law prohibits the mixing of meat and dairy. Look for a "K" or "OU" symbol.
Vague Terminology: If the label simply says “enzymes” or “rennet” without further specification, it is likely of animal origin.
Contact the Manufacturer: If you are in doubt, contacting the manufacturer directly is the most reliable way to confirm the source of their enzymes.

Traditional vs. Vegetarian Mozzarella: A Comparison


Feature	Traditional Mozzarella	Vegetarian Mozzarella
Rennet Source	Animal-derived (from calves)	Microbial (fungi/bacteria), FPC, or vegetable
Cheesemaking Method	Relies on animal rennet for coagulation	Uses microbial rennet or direct acidification
Vegetarian Status	Not Vegetarian	Is Vegetarian (if specified)
Flavor Profile	Complex flavors, especially when aged	Often milder in flavor, especially fresh versions
Common Usage	Authentic Italian recipes	Mass-market products, pizza, fresh balls

Conclusion

While the milk in mozzarella is always a dairy product, its vegetarian status hinges entirely on the type of rennet used during production. The good news is that the vast majority of mozzarella available today, particularly fresh mozzarella and shredded varieties, is made with vegetarian-friendly microbial or genetically engineered enzymes. By learning to read labels carefully and looking for specific indicators like "microbial enzymes" or "vegetarian rennet," individuals can confidently enjoy this delicious cheese without compromising their dietary principles. For those who prefer to be extra cautious, choosing brands with clear vegetarian labeling or relying on naturally acid-coagulated cheeses like paneer and ricotta can provide peace of mind. As the food industry continues to evolve, vegetarian and vegan alternatives are becoming increasingly accessible and delicious, making it easier than ever to make informed choices.

For more resources on identifying vegetarian cheeses, check out this guide from Allrecipes: Here's Why Not All Cheese Is Vegetarian Friendly.

Frequently Asked Questions

Rennet is a complex of enzymes used to curdle milk during cheesemaking. Traditional animal rennet is derived from the stomach lining of young calves, making it a non-vegetarian ingredient because it is a byproduct of the meat industry.

To determine if a mozzarella is vegetarian, you must read the ingredient label. Look for terms like "microbial enzymes," "vegetarian rennet," or "vegetable rennet." If it only says "enzymes" or "rennet," it is likely animal-derived.

No, not all mozzarella cheeses contain animal rennet. While traditional European recipes historically used animal rennet, most mass-produced mozzarella today is made with vegetarian alternatives like microbial or vegetable rennet.

No, many cheeses are made with vegetarian alternatives. Softer, fresh cheeses like cottage cheese and ricotta are often made with acid, while many hard cheeses now use microbial rennet.

Animal rennet is extracted from the stomach lining of young calves. Microbial rennet is produced from specific fungi or bacteria through fermentation, making it a vegetarian-friendly alternative.

Authentic Italian cheeses with a Protected Designation of Origin (PDO) label, such as Parmigiano-Reggiano, are often required by law to use animal rennet. For traditional buffalo mozzarella (mozzarella di bufala), checking for a vegetarian label is important.

Some fresh cheeses like paneer and cream cheese are typically made without rennet at all, using acid instead. Additionally, any cheese certified kosher is guaranteed to be vegetarian.