QUESTION: What types of cheeses are included in the prohibition of gevinas Akum? ANSWER: There are two types of cheese: soft cheese and hard cheese. Until modern times, the most common coagulant that curdled milk into hard cheese was animal rennet, which is typically extracted from the stomach lining of a calf. (Today, microbial rennet, which is extracted from microorganisms, is more common.) Soft cheese is generally made with acids or acid cultures. (Some common acids are vinegar, citric acid and lactic acid.) Poskim agree that hard cheeses (such as Cheddar, Swiss, and Mozzarella) must be gevinas Yisroel to be kosher. Since these can be made with animal rennet, they were certainly included in the gezeira of Chazal.
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