Rennet is usually a natural complex of enzymes produced in any mammalian stomach to digest the mother’s milk, and is often used in the production of cheese. Rennet contains many enzymes, including a proteolyticenzyme (protease) that coagulates the milk, causing it to separate into solids (curds) and liquid (whey). The active enzyme in rennet is called chymosin or rennin but there are also other important enzymes in it, e.g., pepsin or lipase. There are non-animal sources for rennet that are suitable for vegetarian consumption.
The Muslim World consists of 92.5% Sunni Muslims and 7.5% Shia Muslims . Within the Sunni Muslims there are 4 Schools of Thought (Fiqh). These 4 schools are of Hanafi, Shafi, Maliki and Hanbali Fiqh. These schools have do not have any theological difference in faith or fundamentals of Islam. But they have different opinions and interpretations on certain rules of Islam. All 4 schools accept each other to be righteous and honest in their interpretation and recognize each other correct.
In the Hanafi School and the Hanbali School, rennet obtained from an animal slaughtered by a non-Muslim or Muslim in accordance with Islamic law or contrary to it, in all cases is permissible, as long as the animal in question is not a pig. Most well informed people are adamant that rennet, which is used to make cheese, is not derived from pig.
It has been narrated in the major hadith collections from Abdullah ibn Umar (RA) that the Prophet Muhammad (SAW) was brought cheese in Tabuk. He asked for a knife then recited ‘Bismillah’ and cut the cheese.’ (Abu Dawud) Imam Ibn Abi Shaiba narrated through that the grandson of the Prophet (SAW) was asked about the use of cheese prepared by the non Muslims. He said : ‘It is all right. Just put a knife to it, mention Allah’s name, and eat it.’ Imam Ibn Qudama wrote in his book Al-Mughni: “Someone asked Imam Ahmad Ibn Hanbal (Founder of Hanbali Fiqh) about cheese. The Imam replied: ‘You can eat it ‘ But, when asked about the cheese made by the non Muslims, he said: ‘There is an authentic Hadith through al-A`mash that `Amr b. Sharhabîl said that `Umar was asked about cheese and the rennet of illegally slaughtered animal used therein. `Umar instructed him to mention Allah’s name upon it and eat it.”
Kashaaf al Qinaa’ in Hanbali fiqh states that the cheese of the Zoroastrians and other polytheists is allowed even if it is made from rennet of animals they slaughtered. Which means that the cheese made by the People of the Book is also allowed.
Cheese made with animal rennet other than a pig source is halal. The fuqaha explain, however, that it is better to avoid whenever reasonably possible when its source is unknown because of the difference of opinion between the Sunni schools of Islamic Law regarding its permissibility and the doubt therein.
The opinion of the Maliki & Shafi Schools is that such rennet is impure, [refer to: al-Qawânîn al-Fiqhiyyah page 121, al-Majmû`2/588, Nihâyat al-Muhtâj1/244, Sharh Muntahâ al-Iradât 1/31, al-Insâf 92/1, al-Iqnâ` 1/1]. They believed the rennet is impure because it comes from an impure source, the stomach of the illegally slaughtered animal. They say it is a liquid material that touched an impure substance and thus becomes impure.
Imam al-Nawawî said: “It is part of the animal so it is impure, like all the other parts of the animal The Maliki book, Manh al Jaleel says that “Imam Malik disliked cheese because it was made by rennet of animals that are not slaughtered according to Sharia rules (maitah).” The author quotes another Maliki scholar, Abu Ishaaq al
Tunusi as saying that “the cheese of the Zoroastrians is definitely haram but the cheese of the people of the book is halal.” In Sharh al Bahja, a Shafi’I reference, cheese is allowed as long as the rennet is obtained from a properly slaughtered halal animal that is only feeding on milk otherwise the contents of its stomach are najis (impure).
DHCI has adopted the opinion of the Hanafi School, according to which the use of animal rennet (except from pig) is permissible.
However DHCI advises its current clients to use vegetable rennet or microbial rennet specially if this is pheasible.