Is there rennet in mozzarella cheese?: Navigating your dietary choices

November 10, 2025 •

4 min read

It's a common misconception that all cheeses are made with animal products; however, over 90% of the global cheese industry now uses vegetarian alternatives to traditional rennet. When considering your dietary needs, a key question arises: is there rennet in mozzarella cheese? The answer depends entirely on the specific product and its manufacturing process, a crucial detail for vegetarians and those with other dietary restrictions to understand.

Quick Summary

The presence of rennet in mozzarella depends on the specific product, as manufacturers use various types, including animal, microbial, and plant-based coagulants. Identifying vegetarian options requires careful label reading, as many modern cheeses utilize non-animal enzymes for coagulation.

Key Points

Diverse Sources: Rennet, the milk-coagulating enzyme, can come from animal, microbial, vegetable, or genetically engineered (FPC) sources.
Not Always Vegetarian: Traditional mozzarella is made with animal rennet and is not suitable for vegetarians.
Read the Label Carefully: To ensure a mozzarella is vegetarian, look for phrases like 'microbial rennet,' as the term 'enzymes' is ambiguous.
FPC is Common: Fermentation-Produced Chymosin (FPC), a vegetarian-friendly alternative to animal rennet, is used in up to 90% of commercial cheese production today.
Vegan Options Exist: Vegans can choose from mozzarella alternatives made from ingredients like cashews, tofu, or coconut oil.
Acid-Set Cheeses: Some soft, fresh cheeses like ricotta and paneer do not use rennet and instead rely on acid for coagulation, making them vegetarian.

What is Rennet and Why is It Used in Cheesemaking?

Rennet is a complex set of enzymes used in cheesemaking to coagulate milk, separating it into solid curds and liquid whey. This coagulation is a fundamental step for producing most cheeses, providing the characteristic texture and flavor. Traditionally, rennet was extracted from the fourth stomach chamber of young, unweaned ruminant animals, such as calves. This animal-derived rennet contains the enzyme chymosin, which is highly effective at curdling milk. While this has been the standard method for centuries, the demand for cheese, coupled with vegetarian and ethical considerations, has led to the widespread adoption of rennet alternatives.

The Diverse World of Rennet Alternatives

Today, cheesemakers can choose from several types of coagulants, ensuring that consumers with various dietary preferences have options. Understanding the different types is key to making an informed choice:

Animal Rennet: The traditional source, derived from the stomachs of young ruminant animals, most commonly calves. Cheeses made with animal rennet are not considered vegetarian. It is often favored for certain aged cheeses due to its specific enzymatic properties.
Microbial Rennet: Produced by fermenting certain fungi or bacteria in a lab setting. This type is a vegetarian-friendly option and is widely used in commercial cheesemaking, including for many varieties of mozzarella. The quality of microbial rennet has improved significantly, reducing the bitterness sometimes associated with older versions.
Fermentation-Produced Chymosin (FPC): This is a genetically engineered version of chymosin produced by microorganisms like yeast or fungi. It is a vegetarian-friendly, reliable, and cost-effective alternative that is molecularly identical to the chymosin found in calf rennet. FPC now dominates the global rennet market.
Vegetable Rennet: Derived from plants with milk-coagulating properties, such as artichokes, cardoons, or thistles. While suitable for vegetarians, plant-based rennets are less common in industrial production and can sometimes impart a slightly bitter taste to cheese, especially when aged.

How to Confirm Your Mozzarella is Vegetarian-Friendly

For vegetarians, the source of rennet is the most important factor. Since traditional mozzarella can contain animal rennet, it is crucial to check the product label. Many manufacturers who use vegetarian alternatives will explicitly state it, but labeling can sometimes be vague.

Tips for checking the label:

Look for terms like "microbial rennet," "vegetarian rennet," or "non-animal rennet." This confirms that the coagulant is not derived from animal sources.
If the ingredient list only says "enzymes," it is best to be cautious. The term "enzymes" is non-specific and could refer to either animal or vegetarian varieties. In this case, contacting the manufacturer directly is the only way to be certain.
Look for certified vegetarian or vegan labels, which provide the highest assurance that the product meets specific dietary standards.

Comparing Rennet Types in Mozzarella Production

To help clarify the differences, here is a comparison of rennet types commonly used for mozzarella, from a dietary and functional perspective.


Rennet Type	Source	Vegetarian Status	Vegan Status	Flavor Impact	Use in Mozzarella
Animal Rennet	Calf stomach	No	No	Traditional, mild, may improve aged cheese flavor	Traditional Mozzarella, especially for aged varieties
Microbial Rennet	Fungi/bacteria	Yes	No	Neutral to slightly bitter in some aged cheese	Widely used in commercial mozzarella
FPC (Fermentation-Produced Chymosin)	Genetically modified microbes	Yes	No	Neutral, clean flavor	Dominant in industrial mozzarella production
Acid Coagulation	Citric acid, vinegar	Yes	No	Fresh, tangy flavor	Some fresh mozzarella varieties, paneer, ricotta

Vegetarian and Vegan Mozzarella Options

Vegetarians have several options when it comes to enjoying mozzarella:

Microbial or FPC-based Mozzarella: The most common vegetarian option available in supermarkets. These use non-animal enzymes for coagulation and are clearly labeled.
Acid-Set Mozzarella: Some fresh, soft mozzarella is made without rennet, using an acid like citric acid instead. This creates a slightly different texture and flavor but is entirely vegetarian.
Vegan Mozzarella Alternatives: For those following a vegan diet, dairy-free mozzarella is made from plant-based ingredients like cashews, tofu, or coconut oil. These alternatives can often replicate the melt and stretch of traditional cheese, especially on pizza.

Making Informed Dietary Choices

Understanding the cheesemaking process and the different types of rennet is essential for navigating dietary restrictions. For vegetarians, modern cheese production offers an abundance of options beyond traditional animal-based products. For vegans, a growing market of plant-based cheeses provides a satisfying alternative.

Ultimately, the choice comes down to reading labels carefully and understanding the sourcing. For those with specific health concerns, it is wise to research both the production process and the nutritional profile of dairy and non-dairy options. An understanding of the distinctions between these various rennet sources empowers consumers to confidently select products that align with their ethical and dietary needs.

Learn more about the science of rennet coagulation from this overview of enzyme technology: Rennet - an overview.

Frequently Asked Questions

No, not all mozzarella contains rennet. While traditional mozzarella uses rennet, some fresh varieties are made using an acid, like citric acid or vinegar, instead. Many commercially produced mozzarellas also use non-animal coagulants such as microbial rennet or FPC.

Microbial rennet is a vegetarian-friendly coagulant derived from the fermentation of certain molds or fungi. It is a reliable and widely used alternative to traditional animal rennet in commercial cheesemaking.

It is risky to assume cheese with only "enzymes" listed is vegetarian. The term is non-specific and could refer to animal-derived rennet. For confirmation, vegetarians should look for specific labeling like 'microbial rennet' or 'vegetarian rennet,' or contact the manufacturer.

The primary enzyme in both is chymosin, but differences can exist. Some cheesemakers find that traditional animal rennet provides a more classic, complex flavor profile, especially for long-aged cheeses. However, modern microbial rennets have been refined to minimize any noticeable difference in younger cheeses like mozzarella.

FPC stands for Fermentation-Produced Chymosin. It is a genetically engineered version of chymosin produced by modified microorganisms. The final product contains no animal DNA and is considered vegetarian, making it a very common and efficient coagulant in commercial cheese production.

To identify a vegan mozzarella, you must check that the product is completely dairy-free. These products will be labeled as vegan and made from plant-based ingredients such as cashew nuts, tofu, coconut oil, or starches, rather than milk.

Yes, many other cheeses are suitable for vegetarians. Soft, acid-set cheeses like paneer and ricotta are naturally rennet-free. Many hard and semi-hard cheeses are also made with microbial or FPC rennet, and their packaging will typically indicate this.