Verdict Depends on the source
Use this as an educational first check. For products that matter to you, follow an official halal certification or a scholar you trust.
Also called: Animal rennet, Microbial rennet, Vegetable rennet, Chymosin.
What it is
Rennet is the set of enzymes used to curdle milk into cheese. It comes in three forms: traditional animal rennet (from the stomach lining of a calf or other ruminant), microbial rennet (grown from moulds), and vegetable or fermentation-produced (FPC) rennet.
Why it matters for halal
Animal rennet raises the same slaughter question as gelatin: if it comes from an animal that wasn't slaughtered Islamically, most scholars consider it not halal. Microbial and vegetable rennet sidestep the issue entirely because no animal is involved.
The ruling
Cheese made with microbial, fungal or vegetable rennet is widely accepted as halal. Cheese made with animal rennet is halal when the source animal was halal-slaughtered, and doubtful otherwise. A minority view permits animal rennet regardless via the transformation (istihalah) argument, but the mainstream halal-conscious approach is to check the rennet type.
What to do when you're shopping
Look for cheese labelled 'suitable for vegetarians' (a strong hint that microbial/vegetable rennet was used), 'microbial rennet', or carrying a halal mark. If the label only says 'rennet' or 'enzymes' with no source, treat it as doubtful.
Commonly found in
- Hard cheeses
- Some soft cheeses
- Parmesan-style cheese
- Processed cheese