Rennet
The enzyme that curdles milk into cheese. It can be animal, microbial, or fermentation-produced, and Enzymes on a label tells you nothing about which.
Also labelled as: Enzymes, Chymosin, Microbial rennet, Animal rennet, Vegetarian rennet.
What it is
Rennet is a set of enzymes, chiefly chymosin, that coagulates milk so it separates into curds and whey. Traditional animal rennet comes from the fourth stomach of a young ruminant. Microbial rennet is produced by moulds. Fermentation-produced chymosin is made by microbes carrying a copy of the chymosin gene, and is used in a large share of cheese made today.
Why the source matters
Cheese is one of the most common places a diet check quietly fails. A cheese can be entirely vegetarian in every ingredient except the coagulant, and coagulants are frequently declared only as Enzymes. That single word covers both a calf-derived enzyme and a laboratory-fermented one, so the label does not resolve the question that matters.
Rennet by dietary profile
| Profile | Verdict | Why |
|---|---|---|
| Halal | Depends on the source | Microbial and fermentation-produced chymosin are generally accepted. Animal rennet depends on the source animal and its slaughter, and authorities differ. Certification is the practical answer. |
| Kosher | Depends on the source | Kosher cheese requires supervision, and the coagulant is part of what supervision covers. Microbial coagulants are common in kosher cheese production. An unmarked cheese is unresolved regardless of how the ingredients read. |
| Vegetarian | Depends on the source | Microbial and fermentation-produced chymosin are suitable. Animal rennet is not. If the label says only Enzymes, the answer is unknown. |
| Vegan | Not suitable | The coagulant may be suitable, but the milk it acts on is not. Cheese is not vegan regardless of rennet type. |
| Pescatarian | Depends on the source | Same position as vegetarian: it turns on whether the coagulant is animal-derived. |
| Hindu vegetarian | Depends on the source | Animal rennet is not suitable, and bovine-derived rennet carries additional significance. Microbial coagulants are generally accepted. |
Related: Is rennet halal? answers that question on its own page, with what to look for on a package and where authorities differ.
How to spot it on a label
- Vegetarian rennet, microbial rennet, or microbial enzymes: plant-compatible coagulant.
- Animal rennet or simply Rennet: usually animal-derived.
- Enzymes with no qualifier: genuinely ambiguous, and common.
- A vegetarian society mark on cheese is a stronger signal than the ingredient list.
What PlatePal cannot determine
Known limits for rennet
- Which coagulant was used when the label says only Enzymes.
- Whether a cheese made abroad follows the same naming conventions as a domestic one.
- Whether animal rennet in an otherwise certified product was itself certified.
When any of these apply, PlatePal returns Insufficient data rather than a guess. A scan that says it does not know is doing its job.
Sources
Regulations change and authorities differ. This page is general information, not a religious or medical ruling. Last reviewed 2026-09-12.
Related ingredients
- Gelatin: A collagen protein set from animal hide and bone. Whether it fits your diet depends entirely on which animal it came from, and labels rarely say.
- Carmine: A red colour made from cochineal insects. It must be named on US labels, which makes it one of the easier additives to spot.
- Whey: The liquid left after milk curdles into cheese. It is always a milk allergen, and it inherits whichever coagulant made the cheese.
Back to the ingredient guide, or see how PlatePal checks a whole product with the halal, kosher, and allergen scanners.