What is Rennet and Why is it in Cheese?
Rennet is a crucial enzyme in cheesemaking, responsible for coagulating milk into solid curds, which are then separated from the liquid whey. This coagulation is an essential step in producing many types of cheese, especially aged, hard varieties. Without rennet, cheese would not achieve its characteristic texture and firmness.
For centuries, the primary source of rennet was the stomach lining of young, unweaned mammals like calves, lambs, and goats. This enzyme, predominantly chymosin, aids the young animal in digesting its mother's milk. Traditionally, obtaining this animal rennet was a byproduct of the meat industry, specifically veal production.
The Problem with Animal Rennet for Vegetarians
A vegetarian diet, particularly a lacto-vegetarian one, includes dairy but avoids any products that result from the slaughter of an animal. Since traditional animal rennet is derived from the stomach lining of slaughtered young animals, it is not considered vegetarian. For this reason, vegetarians who strictly adhere to their dietary principles cannot consume cheese that is made with animal rennet.
This is a common point of confusion, as many people assume that because dairy cheese is not meat, it is automatically vegetarian. However, the use of animal rennet places certain cheeses, particularly some European and artisan varieties, outside the scope of a vegetarian diet.
Vegetarian-Friendly Rennet Alternatives
Today, vegetarians have many options because the cheese industry has developed effective, non-animal alternatives to traditional rennet. These include:
- Microbial Rennet: This is the most common vegetarian alternative, produced by fermenting certain fungi or molds like Rhizomucor miehei. It is widely used in modern commercial cheesemaking, produces consistent results, and is suitable for most cheeses.
- Vegetable Rennet: Derived from plants with coagulating properties, such as thistles, nettles, or figs. This type is more common in artisanal cheesemaking and can sometimes impart a slightly bitter taste to aged cheeses.
- Fermentation-Produced Chymosin (FPC): This is a genetically engineered version of chymosin, where the gene for the enzyme is implanted into microorganisms like yeast or bacteria. The microbes then produce large quantities of pure chymosin. FPC is highly efficient, cost-effective, and now dominates the global market for rennet. While suitable for vegetarians, some may avoid FPC due to its use of genetically modified organisms in production.
How to Identify Vegetarian Cheese
Determining if a cheese is truly vegetarian requires careful inspection, as labeling regulations vary by country. Here are the key indicators to look for:
- Check the Label: Look for specific terms like “vegetarian rennet,” “microbial enzymes,” “vegetable enzymes,” or “non-animal rennet” in the ingredients list. If the label only lists “enzymes,” it's safer to assume it contains animal rennet unless specified otherwise.
- Kosher Certification: Kosher law prohibits mixing meat and dairy. Therefore, any cheese with a kosher certification symbol (like K, U, or a star) will not use animal rennet.
- Consider the Cheese Type: Soft cheeses like ricotta, cottage cheese, and paneer are often coagulated with acid (e.g., vinegar or lemon juice) and do not require rennet at all, making them safe for vegetarians. Many mass-produced cheeses in the US use microbial or FPC rennet, while traditional European cheeses like Parmigiano-Reggiano often require animal rennet by law for official designation.
- Ask the Cheesemonger: When purchasing artisan cheese from a specialty shop, the staff can provide definitive information on the type of rennet used in their products.
Comparison of Rennet Types
| Feature | Animal Rennet | Microbial Rennet | Fermentation-Produced Chymosin (FPC) | Vegetable Rennet |
|---|---|---|---|---|
| Source | Stomach of young ruminants (calves, lambs) | Fungi and molds (e.g., Rhizomucor miehei) | Genetically modified microbes | Plants (e.g., thistle, nettles, figs) |
| Vegetarian Status | No (derived from slaughtered animals) | Yes (non-animal source) | Yes (non-animal source) | Yes (plant source) |
| Flavor Impact | Often provides a full, complex flavor profile | Can sometimes produce a slightly bitter flavor in aged cheese | Cleaner, consistent flavor profile, similar to animal rennet | Can be inconsistent; may produce bitterness in aged cheeses |
| Common Use | Traditional, hard European cheeses (e.g., Parmigiano-Reggiano) | Most mass-produced commercial cheeses | Dominant form of rennet globally | Artisan and specialty cheeses (e.g., Portuguese thistle cheeses) |
Conclusion
Understanding the source of rennet is crucial for any vegetarian who wishes to consume cheese. While animal rennet is a non-vegetarian ingredient derived from animal slaughter, the widespread availability of microbial, vegetable, and FPC alternatives means a vegetarian diet can still include a wide variety of delicious cheeses. By carefully reading labels, looking for kosher certification, and knowing which types of cheeses are generally safe, vegetarians can confidently make informed choices about their food.
For more information on the distinctions between different vegetarian diets, visit the Wikipedia page on lacto-vegetarianism, which specifically mentions avoiding cheese with animal rennet.
