Understanding Rennet in Cheesemaking
Rennet is a complex set of enzymes used in cheesemaking to coagulate milk, separating the solid curds from the liquid whey. This crucial step forms the base for most cheeses, including mozzarella. Traditionally, rennet was harvested from the stomach lining of young ruminant mammals, such as calves, lambs, and kids. The active enzyme, chymosin, aids the animal in digesting milk and is highly effective at curdling casein protein. However, changing dietary preferences and the search for more consistent and cost-effective production methods have led to the development of several alternatives.
The Different Types of Rennet
Rennet's use is not universal, and cheesemakers have adopted a variety of other coagulants. This variety is the key to why not all mozzarella contains animal rennet. Modern production relies heavily on alternatives.
Animal Rennet
This is the traditional form of rennet, most commonly extracted from the fourth stomach of young ruminants. It is prized for its specific enzymatic profile, which can contribute to the flavor and texture of certain aged cheeses. Many Protected Designation of Origin (PDO) cheeses, like Parmigiano-Reggiano, are legally required to use animal rennet. Its availability has declined over time, leading to alternatives.
Microbial Rennet
This is a vegetarian alternative produced by fermenting specific fungi, molds, or yeasts in a controlled lab environment. Microbial rennet has become very common in modern, large-scale cheese production due to its consistency, cost-effectiveness, and suitability for vegetarian diets. Improved purification processes have significantly reduced the bitter aftertaste once associated with it.
Fermentation-Produced Chymosin (FPC)
Also known as 'vegetarian rennet' in some ingredient lists, FPC is a highly purified, genetically engineered version of chymosin. It is made by taking the gene for calf chymosin and inserting it into microorganisms, which then produce the enzyme. This results in a coagulant that is chemically identical to calf rennet but is produced without any animal inputs, making it vegetarian-friendly. FPC now holds a significant portion of the global rennet market.
Plant-Based Rennet
This type of rennet is derived from the enzymes of various plants, including fig juice, thistles, and cardoons. While historically used and still employed in some artisanal cheese production, plant-based rennets are less common in modern commercial mozzarella production.
Is All Mozzarella Made the Same?
No, all mozzarella is not created equal, and the type of rennet used depends heavily on the production method and style. The distinction is most clear between fresh and low-moisture varieties.
Fresh Mozzarella vs. Low-Moisture Mozzarella
- Traditional Fresh Mozzarella: The famed mozzarella di bufala is traditionally made with animal rennet from water buffalo milk, though cow's milk versions (fior di latte) are also common. For truly authentic, artisanal Italian fresh mozzarella, assume it contains animal rennet unless specifically stated otherwise. However, many modern fresh mozzarella products found in typical grocery stores use microbial or FPC rennet to be suitable for vegetarians. Fresh mozzarella is soft, mild, and packed in liquid.
- Low-Moisture Mozzarella: This is the block or pre-shredded mozzarella commonly used on pizzas and in casseroles. A significant proportion of this mass-produced mozzarella is made using non-animal rennet, particularly microbial rennet or FPC. The shift occurred partly due to a rennet shortage in the 1970s and 80s as the pizza industry grew exponentially. Since manufacturers want to appeal to a wider audience, including vegetarians, many use non-animal coagulants.
Comparison of Rennet Types
| Feature | Animal Rennet | Microbial Rennet | FPC (Vegetarian) |
|---|---|---|---|
| Origin | Stomach of young ruminants | Fungi, molds, and yeasts | Genetically engineered microbes |
| Cost | More expensive | Cheaper to produce | Consistent and large-scale |
| Consistency | Can vary slightly | Highly consistent | Highly consistent |
| Effect on Flavor | Associated with traditional flavors, especially in aged cheeses | Some older versions had a bitter aftertaste; modern versions are improved | Chemically identical to calf chymosin, minimal flavor impact |
| Suitability for Vegans | No | Yes (if no other animal products are used) | Yes (if no other animal products are used) |
How to Identify Vegetarian Mozzarella
Since it's not always obvious, here's how to ensure your mozzarella is vegetarian:
- Check the Label: The ingredient list is your best friend. Look for specific terms like "vegetarian rennet," "microbial rennet," "non-animal rennet," or "vegetarian enzymes". Some brands, like Cello, proudly state they only use microbial rennet.
- Beware of Ambiguous Terms: If the label simply says "enzymes," it is highly likely that animal-derived rennet was used. This is common for traditional and artisanal European cheeses.
- Look for Vegetarian or Kosher Certifications: Certified kosher cheese is always vegetarian because the use of animal rennet with milk is a violation of kashrut laws. Likewise, official vegetarian society logos (like the V-Label) confirm the cheese is free from animal rennet.
- Research the Brand: If you are still unsure, visit the manufacturer's website or contact their customer service department. Many brands provide detailed information on their production practices online. For instance, Godminster confirms they use only microbial rennet.
- Consider Vegan Alternatives: For a guaranteed animal-free option, plant-based mozzarella substitutes exist. These are made from ingredients like cashews, almonds, or starches and are clearly labeled as vegan.
Conclusion
To conclude, the assumption that all mozzarella contains animal rennet is a common misconception. While traditional, artisanal varieties—especially those from specific Italian regions—may use animal rennet, most of the mozzarella found in modern supermarkets does not. The widespread adoption of vegetarian alternatives like microbial and FPC rennet has made it easier for vegetarians to enjoy mozzarella. The key is to be an informed consumer by carefully reading ingredient labels and looking for specific certifications. By doing so, you can confidently choose a mozzarella that aligns with your dietary preferences, whether for your pizza, caprese salad, or other favorite dishes.
