Ingredient
Is rennet kosher?
Rennet is one of the main reasons cheese needs supervision. It’s classically animal-derived, and you can’t tell from the label which kind a given cheese used.
Why it’s not that simple
Rennet sits at the center of the cheese question:
- Rennet is the enzyme that curdles milk into cheese. Traditional rennet comes from the stomach lining of animals — often non-kosher ones.
- Microbial and vegetable rennet exist and can be acceptable, but the label almost never tells you which was used.
- Even with acceptable rennet, hard cheese still raises gevinas Yisroel — a separate requirement. See: is cheese kosher? →
- So rennet is a certification question by nature — the ingredient panel cannot answer it.
How to actually know
The only reliable way to know a specific product is kosher is a trusted kosher symbol on the package. Learn the designations — D (dairy) and Pareve (no meat or dairy) — and never rely on the ingredient panel, the brand’s reputation, or the name on the front. When you’re unsure about a product or a symbol you don’t recognize, ask your rav.
And it can change
A producer may switch coagulants between runs — the hechsher is what tracks it.
For shoppers
Look for a reliable hechsher on cheese, and know your practice on gevinas Yisroel — ask your rav.
For manufacturers
Coagulants determine whether an entire cheese line can be certified. See our cheese certification →
Educational only — not a halachic ruling. Kosher status depends on the specific product and its certification, and can change. Verify the symbol and consult your rav. Reviewed by the Pure K rabbinic staff.