The enzyme that sets cheese: which kinds are acceptable and what scholars say
Rennet is doubtful (mushbooh), and the answer depends on which kind it is. Rennet from microbes, plants or fermentation is permissible according to the sources we read. Rennet from a pig is forbidden. Rennet from a lawful animal that was not slaughtered in the Islamic way is a point on which scholars differ, and that is the case that matters most for ordinary cheese.
The IslamOnline Fiqh answer we read says that some scholars hold such rennet to be pure and permissible, while the majority hold it to be impure, because the stomach becomes impure when the animal dies unlawfully. A Muftionline answer in the Hanafi tradition advises refraining from cheese made with animal rennet from animals not slaughtered according to Shariah.
Rennet is a set of enzymes that curdle milk, separating it into curds, which become cheese, and whey. Traditional rennet comes from the inner lining of the fourth stomach of young nursing calves, as a by-product of veal production. The general reference on rennet says that less than five per cent of US cheese uses animal rennet today.
Microbial rennet is made from moulds grown in a fermenter. Fermentation-produced chymosin is the same enzyme as calf chymosin, made by inserting the gene into bacteria, fungi or yeast; the reference says it has been sold since 1990 and held about 90 per cent of the global rennet market by 2017. Vegetable rennet can come from plants such as fig juice, thistles and cardoons. The reference adds that cheeses made with fermentation-produced chymosin can be certified both kosher and halal.
| Rennet type | Status | Notes |
|---|---|---|
| Microbial rennet | Halal | Permitted on all the sources we read; check any non-halal growth medium |
| Vegetable rennet | Halal | Plant-based |
| Fermentation-produced chymosin | Halal | Can be certified halal; check the product |
| Calf rennet, halal-slaughtered | Halal | Permissible; certified products only |
| Calf rennet, not halal-slaughtered | Doubtful | Scholars differ; many advise refraining |
| Pig rennet | Haram | Forbidden |
The Muftionline answer we read explains that Abu Hanifah permitted rennet from animals not slaughtered according to Shariah, citing certain narrations, while Abu Yusuf and Muhammad prohibited it. The disagreement concerned traditional rennet taken from curdled milk in the stomach of a calf slaughtered a few hours after nursing. The answer says that today rennet is impermissible from animals not slaughtered according to Shariah, according to all the Hanafi Imams, because modern extraction takes it from the stomach lining, which it treats as impure. Rennet from halal-slaughtered animals, and plant or microbial sources, are permissible. Its practical advice is that it is safest to refrain on account of the difference of opinion. That page does not discuss the Shafi'i, Maliki or Hanbali positions, so we do not describe them.
This answer does not name the scholars or schools involved. It says that for a lawful animal not slaughtered correctly, some prominent scholars hold the rennet to be pure and the majority hold it to be impure. It states that plant-based and microbial rennets are unanimously permissible across all schools and that rennet from a pig is unanimously prohibited. Its practical advice is to look for labels such as "microbial rennet", "vegetable rennet" or "suitable for vegetarians", and to treat plain "rennet" or "animal enzymes" as usually animal.
Rennet is used in cheese, and sometimes in desserts such as junket and some cheese-flavoured snacks. Whey from rennet-set cheese goes into many other foods; see our guide to whey. Animal enzymes such as pepsin may be present in rennet blends; see our pepsin guide.
Islamic teaching on doubtful matters is the basis for how we label these ingredients. A well-known hadith, recorded in the collections of al-Bukhari and Muslim, says that the halal is clear and the haram is clear, and between them are doubtful matters that many people do not know about. Scholars generally draw two practical points from it. First, you are encouraged to avoid what you have real reason to doubt, as far as you reasonably can. Second, this is not a call to be anxious about every additive: where there is no real reason to doubt, most scholars do not ask you to investigate beyond what is reasonable.
That is why our "doubtful" label means check if you can, not assume it is forbidden. A halal logo, a clear source on the label, or a short email to the maker will usually settle the matter. If you follow a particular madhab or scholar, their guidance comes first.
Microbial, plant and fermentation-produced rennet are permitted. Animal rennet depends on the animal and slaughter, and scholars differ. Pig rennet is forbidden.
Scholars differ. The Hanafi Muftionline answer we read advises refraining from cheese made with rennet from animals not slaughtered according to Shariah. The IslamOnline Fiqh answer says some prominent scholars hold such rennet pure, while the majority do not.
Look for "microbial rennet", "vegetable rennet" or "suitable for vegetarians" on the label, or a halal logo. Plain "rennet" or "animal enzymes" usually indicates animal origin.
Yes. Plant-based and microbial rennets are unanimously permissible across all schools according to the IslamOnline Fiqh answer.
The rennet is usually fine, but other ingredients such as lysozyme (egg) or flavourings can still matter. A halal logo covers everything.
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✦ Open Free Halal CheckerThese are the pages we read for this guide. We summarise what each says; we do not claim these bodies endorse Afiya AI.